Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase fusion genes: A workshop report with focus on novel entities and a literature review including paediatric cases

Myeloid/lymphoid neoplasms with eosinophilia (M/LN-eo) and tyrosine kinase (TK) gene fusions are a rare group of haematopoietic neoplasms with a broad range of clinical and morphological presentations. Paediatric cases have increasingly been recognised. Importantly, not all appear as a chronic myeloid neoplasm and eosinophilia is not always present. In addition, standard cytogenetic and molecular methods may not be sufficient to diagnose M/LN-eo due to cytogenetically cryptic aberrations. Therefore, additional evaluation with fluorescence in-situ hybridisation and other molecular genetic techniques (array-based comparative genomic hybridisation, RNA sequencing) are recommended for the identification of specific TK gene fusions. M/LN-eo with JAK2 and FLT3-rearrangements and ETV6::ABL1 fusion were recently added as a formal member to this category in the International Consensus Classification (ICC) and the 5th edition of the WHO classification (WHO-HAEM5). In addition, other less common defined genetic alterations involving TK genes have been described. This study is an update on M/LN-eo with TK gene fusions with focus on novel entities, as illustrated by cases submitted to the Bone Marrow Workshop, organised by the European Bone Marrow Working Group (EBMWG) within the frame of the 21st European Association for Haematopathology congress (EAHP-SH) in Florence 2022. A literature review was performed including paediatric cases of M/LN-eo with TK gene fusions.

A vector-encoded bispecific killer engager to harness virus-activated NK cells as anti-tumor effectors

Treatment with oncolytic measles vaccines (MV) elicits activation of immune cells, including natural killer (NK) cells. However, we found that MV-activated NK cells show only modest direct cytotoxic activity against tumor cells. To specifically direct NK cells towards tumor cells, we developed oncolytic measles vaccines encoding bispecific killer engagers (MV-BiKE) targeting CD16A on NK cells and carcinoembryonic antigen (CEA) as a model tumor antigen. MV-BiKE are only slightly attenuated compared to parental MV and mediate secretion of functional BiKE from infected tumor cells. We tested MV-BiKE activity in cocultures of colorectal or pancreatic cancer cells with primary human NK cells. MV-BiKE mediate expression of effector cytokines, degranulation and specific anti-tumor cytotoxicity by NK cells. Experiments with patient-derived pancreatic cancer cultures indicate that efficacy of MV-BiKE may vary between individual tumors with differential virus permissiveness. Remarkably, we confirmed MV-BiKE activity in primaryhuman colorectal carcinoma specimens with autochthonous tumor and NK cells.This study provides proof-of-concept for MV-BiKE as a novel immunovirotherapy to harness virus-activated NK cells as anti-tumor effectors.

The fatal trajectory of pulmonary COVID-19 is driven by lobular ischemia and fibrotic remodelling

BACKGROUND

COVID-19 is characterized by a heterogeneous clinical presentation, ranging from mild symptoms to severe courses of disease. 9-20% of hospitalized patients with severe lung disease die from COVID-19 and a substantial number of survivors develop long-COVID. Our objective was to provide comprehensive insights into the pathophysiology of severe COVID-19 and to identify liquid biomarkers for disease severity and therapy response.

METHODS

We studied a total of 85 lungs (n = 31 COVID autopsy samples; n = 7 influenza A autopsy samples; n = 18 interstitial lung disease explants; n = 24 healthy controls) using the highest resolution Synchrotron radiation-based hierarchical phase-contrast tomography, scanning electron microscopy of microvascular corrosion casts, immunohistochemistry, matrix-assisted laser desorption ionization mass spectrometry imaging, and analysis of mRNA expression and biological pathways. Plasma samples from all disease groups were used for liquid biomarker determination using ELISA. The anatomic/molecular data were analyzed as a function of patients' hospitalization time.

FINDINGS

The observed patchy/mosaic appearance of COVID-19 in conventional lung imaging resulted from microvascular occlusion and secondary lobular ischemia. The length of hospitalization was associated with increased intussusceptive angiogenesis. This was associated with enhanced angiogenic, and fibrotic gene expression demonstrated by molecular profiling and metabolomic analysis. Increased plasma fibrosis markers correlated with their pulmonary tissue transcript levels and predicted disease severity. Plasma analysis confirmed distinct fibrosis biomarkers (TSP2, GDF15, IGFBP7, Pro-C3) that predicted the fatal trajectory in COVID-19.

INTERPRETATION

Pulmonary severe COVID-19 is a consequence of secondary lobular microischemia and fibrotic remodelling, resulting in a distinctive form of fibrotic interstitial lung disease that contributes to long-COVID.

FUNDING

This project was made possible by a number of funders. The full list can be found within the Declaration of interests / Acknowledgements section at the end of the manuscript.

Human colon organoids reveal distinct physiologic and oncogenic Wnt responses

Constitutive Wnt activation upon loss of Adenoma polyposis coli (APC) acts as main driver of colorectal cancer (CRC). Targeting Wnt signaling has proven difficult because the pathway is crucial for homeostasis and stem cell renewal. To distinguish oncogenic from physiological Wnt activity, we have performed transcriptome and proteome profiling in isogenic human colon organoids. Culture in the presence or absence of exogenous ligand allowed us to discriminate receptor-mediated signaling from the effects of CRISPR/Cas9-induced APC loss. We could catalog two nonoverlapping molecular signatures that were stable at distinct levels of stimulation. Newly identified markers for normal stem/progenitor cells and adenomas were validated by immunohistochemistry and flow cytometry. We found that oncogenic Wnt signals are associated with good prognosis in tumors of the consensus molecular subtype 2 (CMS2). In contrast, receptor-mediated signaling was linked to CMS4 tumors and poor prognosis. Together, our data represent a valuable resource for biomarkers that allow more precise stratification of Wnt responses in CRC.

CD74 regulates complexity of tumor cell HLA class II peptidome in brain metastasis and is a positive prognostic marker for patient survival

Despite multidisciplinary local and systemic therapeutic approaches, the prognosis for most patients with brain metastases is still dismal. The role of adaptive and innate anti-tumor response including the Human Leukocyte Antigen (HLA) machinery of antigen presentation is still unclear. We present data on the HLA class II-chaperone molecule CD74 in brain metastases and its impact on the HLA peptidome complexity.We analyzed CD74 and HLA class II expression on tumor cells in a subset of 236 human brain metastases, primary tumors and peripheral metastases of different entities in association with clinical data including overall survival. Additionally, we assessed whole DNA methylome profiles including CD74 promoter methylation and differential methylation in 21 brain metastases. We analyzed the effects of a siRNA mediated CD74 knockdown on HLA-expression and HLA peptidome composition in a brain metastatic melanoma cell line.We observed that CD74 expression on tumor cells is a strong positive prognostic marker in brain metastasis patients and positively associated with tumor-infiltrating T-lymphocytes (TILs). Whole DNA methylome analysis suggested that CD74 tumor cell expression might be regulated epigenetically via CD74 promoter methylation. CD74high and TILhigh tumors displayed a differential DNA methylation pattern with highest enrichment scores for antigen processing and presentation. Furthermore, CD74 knockdown in vitro lead to a reduction of HLA class II peptidome complexity, while HLA class I peptidome remained unaffected.In summary, our results demonstrate that a functional HLA class II processing machinery in brain metastatic tumor cells, reflected by a high expression of CD74 and a complex tumor cell HLA peptidome, seems to be crucial for better patient prognosis.

Netrin-1 expression is an independent prognostic factor for poor patient survival in brain metastases

The multifunctional molecule netrin-1 is upregulated in various malignancies and has recently been presented as a major general player in tumorigenesis leading to tumor progression and maintenance in various animal models. However, there is still a lack of clinico-epidemiological data related to netrin-1 expression. Therefore, the aim of our study was to elucidate the association of netrin-1 expression and patient survival in brain metastases since those constitute one of the most limiting factors for patient prognosis. We investigated 104 brain metastases cases for netrin-1 expression using in-situ hybridization and immunohistochemistry with regard to clinical parameters such as patient survival and MRI data. Our data show that netrin-1 is strongly upregulated in most cancer subtypes. Univariate analyses revealed netrin-1 expression as a significant factor associated with poor patient survival in the total cohort of brain metastasis patients and in sub-entities such as non-small cell lung carcinomas. Interestingly, many cancer samples showed a strong nuclear netrin-1 signal which was recently linked to a truncated netrin-1 variant that enhances tumor growth. Nuclear netrin-1 expression was associated with poor patient survival in univariate as well as in multivariate analyses. Our data indicate both total and nuclear netrin-1 expression as prognostic factors in brain metastases patients in contrast to other prognostic markers in oncology such as patient age, number of brain metastases or Ki67 proliferation index. Therefore, nuclear netrin-1 expression constitutes one of the first reported molecular biomarkers for patient survival in brain metastases. Furthermore, netrin-1 may constitute a promising target for future anti-cancer treatment approaches in brain metastases.

Diagnosis according to World Health Organization determines the long-term prognosis in patients with myeloproliferative neoplasms treated with anagrelide: results of a prospective long-term follow-up

OBJECTIVES

During long term follow-up of a cohort of patients with essential thrombocythemia (ET) and polycythemia vera (PV) a higher than expected incidence of myelofibrosis (MF) was noted. In order to test if the explanation could be found in the diagnostic criteria a re-evaluation of diagnosis using the 2008 WHO diagnostic criteria for ET and MF was performed.

METHODS

This prospective study of 60 patients with ET and PV was set up in 1998 to evaluate the long-term efficacy and tolerability of anagrelide treatment. Bone marrow trephine biopsies were requested from study start, after 2 and 7 years of follow-up. A blinded re-evaluation of the bone marrow trephines was performed. The 2008 WHO bone marrow criteria were used for diagnosis and fibrosis grading.

RESULTS

Of 40 patients with an initial diagnosis of ET, 21 were confirmed as 'true ET' whereas 17 were reclassified as primary myelofibrosis (PMF) (12 PMF-0, 3 PMF-1, 2 PMF-2) and 2 as myeloproliferative neoplasms of uncertain origin. After 7 years of follow-up, 19 of 21 patients with 'true ET' were alive, none had transformed to MF, leukemia, or myelodysplastic syndrome. In contrast, 4/17 patients reclassified as PMF had died, two patients transformed to myelodysplastic syndrome and 7 patients progressed to overt MF.

DISCUSSION

We conclude that a blinded re-evaluation of bone marrow trephines from study start and after 7 years of follow-up using 2008 World Health Organization criteria was able to differentiate between true ET and PMF with a marked difference in follow-up outcome.

Abstract 2717: Detection of Merkel cell polyomavirus in chronic lymphocytic leukemia cells by fluorescence in situ hybridization (FISH)

Background: Merkel cell polyomavirus (MCPyV) is detected in approximately 80% of Merkel cell carcinomas (MCC). A number of previous studies have shown that MCC patients are at a significantly increased risk to develop chronic lymphocytic leukemia (CLL) and vice versa. Until recently, clonal integration and truncating mutations of the Large T antigen (LTAg) of MCPyV were restricted to MCC. We have recently reported the presence of the MCPyV in highly purified tumor cells of CLL (n = 19/70, 27.1%) (Blood. 2010 Sep 3). Of these, six revealed a novel 246 bp deletion in the helicase gene of the LTAg. The presence of MCPyV was confirmed by immunohistochemistry.

Material and Method: Here we aimed to determine the presence of MCPyV by fluorescence in situ hybridization (FISH) analysis in CLL cells in order to evaluate whether MCPyV was integrated or episomal. For this purpose we performed FISH analysis as previously described (Int J Cancer. 2005, 115:419-428) using the MCPyV genome as FISH probe. We tested 2 of the previously reported MCPyV positive CLL cases (EDTA decalcified bone marrow trephines) and MCPyV-positive MCC (n = 5). In addition, we tested MCPyV-negative tumors, e.g. breast and colon cancers. All tissues were formalin-fixed and paraffin-embedded.

Results: Specific MCPyV DNA by FISH analysis was detected in the nuclei of MCPyV-positive CLL and MCC cells. In contrast to particularly punctate FISH signals in MCC indicating viral integration, the nuclear FISH signals of the CLL cases revealed especially granular signals, indicative for integrated MCPyV DNA together with transcribed viral RNA (Int J Cancer. 2008, 122:2656-2664). No signals were obtained by MCPyV FISH in breast or colon cancer specimens.

Conclusion: The specific detection of MCPyV in CLL cells further supports our previous report of a possible involvement of MCPyV in a significant subset of CLL. The specific but rather granular nuclear FISH signals in MCPyV positive CLL cells needs further study to evaluate if it is also generated by co-existing episomal virus copies, by viral RNA or by the decalcification process. In addition, more CLL cases will be analyzed for the presence of MCPyV.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2717. doi:10.1158/1538-7445.AM2011-2717

Pomalidomide is active in the treatment of anemia associated with myelofibrosis

PURPOSE

Thalidomide and lenalidomide can alleviate anemia in myelofibrosis. However, their value is undermined by their respective potential to cause peripheral neuropathy and myelosuppression. We therefore evaluated the safety and therapeutic activity of another immunomodulatory drug, pomalidomide.

METHODS

In a phase II randomized, multicenter, double-blind, adaptive design study, four treatment arms were evaluated: pomalidomide (2 mg/d) plus placebo, pomalidomide (2 mg/d) plus prednisone, pomalidomide (0.5 mg/d) plus prednisone, and prednisone plus placebo. Pomalidomide was administered for up to 12 28-day treatment cycles. Prednisone (30 mg/d) was given in a tapering dose schedule during the first three cycles. Response was assessed by International Working Group criteria.

RESULTS

Eighty-four patients with myelofibrosis-associated anemia were randomly assigned to the aforementioned treatment arms: 22, 19, 22, and 21, respectively. Response in anemia was documented in 20 patients, including 15 who became transfusion independent. Response rates in the four treatment arms were 23% (95% CI, 5% to 41%), 16% (95% CI, 0% to 33%), 36% (95% CI, 16% to 56%), and 19% (95% CI, 2% to 36%). The corresponding figures for patients receiving > or = 3 cycles of treatment (n = 62) were 38%, 23%, 40%, and 25%. Response to pomalidomide with or without prednisone was durable (range, 3.2 to 16.9+ months) and significantly better in the absence of leukocytosis (37% v 8%; P = .01); JAK2V617F or cytogenetic status did not affect response. Grade > or = 3 toxicities were infrequent and included (in each treatment arm) neutropenia (9%; 16%; 5%; 5%), thrombocytopenia (14%; 16%; 9%; 5%), and thrombosis (9%; 5%; 0%; 0%).

CONCLUSION

Pomalidomide therapy at 0.5 or 2 mg/d with or without an abbreviated course of prednisone is well tolerated in patients with myelofibrosis and active in the treatment of anemia.

Myelofibrosis – What’s in a Name?

OBJECTIVE

Myelofibrosis (MF) implies an increase in the bone marrow (BM) fiber content without referring to quantity or quality (reticulin vs. collagen).

METHODS

This review on chronic myeloproliferative disorders is based on initial and sequential BM biopsies, clinical data and follow-up examinations. A semiquantitative grading system for MF approved by a panel of experts was applied.

RESULTS

In chronic myelogenous leukemia, minimal reticulin to advanced collagen MF is detectable at presentation in about 30% of patients. Significant correlations between BM and clinical features, but especially prognosis, are evident. Chronic idiopathic MF includes a prodromal stage showing no or little reticulin and no relevant MF with myeloid metaplasia (MMM). A stepwise evolution is demonstrable and associated with corresponding clinical data. Usually MMM is the diagnostic guideline for this disorder and consequently early stages with accompanying thrombocytosis may clinically mimic essential thrombocythemia. MF of various degrees may be observed in polycythemia vera depending on the progress of disease. Terminal stages (spent phase) reveal overt collagen corresponding with MMM. If diagnosis of essential thrombocythemia regards characteristic BM features, no relevant MF is seen at presentation and transformation into MMM is neglectable for many years.

CONCLUSION

To recognize dynamics of the disease process in chronic myeloproliferative disorders, an easily to reproduce scoring system for MF has been proposed. The clinical diagnosis of MMM does not include initial-early reticulin MF and therefore fails to detect prodromal stages.

Dualism of mixed chimerism between hematopoiesis and stroma in chronic idiopathic myelofibrosis after allogeneic stem cell transplantation

Scant knowledge exists concerning lineage-restricted mixed chimerism (mCh) after allogeneic peripheral blood stem cell transplantation (PSCT) in patients with chronic idiopathic myelofibrosis (CIMF). Following a sex-mismatched PSCT, a combined immunopheno- and genotyping by fluorescence in-situ hybridization (FISH) was performed on sequential bone marrow (BM) biopsies at standardized intervals. Results were compared with PCR analysis of corresponding peripheral blood samples in five patients. According to FISH, pretransplant specimens revealed a gender congruence of more than 99%, while in the first three months the total BM exhibited a persistent fraction of host cells (30% to 40%) with a tendency to decline after about one year. It is noteworthy that the majority of endothelial cells maintained a recipient origin, whereas CD34+ progenitors and especially CD61+ megakaryocytes exhibited only very few host-derived cells. In keeping with the prevalence of donor cells in the hematopoietic compartment, PCR analysis of peripheral blood cells displayed a non-significant degree of mCh. In conclusion, according to FISH and PCR analysis, successful PSCT in CIMF results in an almost complete chimeric (donor-derived) state of the hematopoietic cell population. The non-transplantable stromal compartment includes the vascular endothelium with a predominance of recipient cells. The minimal mCh of this population implies probably a donor-derived origin (endothelial progenitor cells).

Myelofibrosis in chronic myeloproliferative disorders--dynamics and clinical impact

In chronic myeloproliferative disorders, presenting or evolving myelofibrosis (MF) is associated with significant morbidity and mortality. A systematically conducted evaluation of previous studies and data from our own material reveals a strikingly expressed heterogeneity of findings. Assessment of MF should be performed by a recently established semiquantitative scoring system regarding quantity and quality (reticulin versus collagen). It is important to differentiate between a fiber increase in bone marrow specimens and the clinical diagnosis that is explicitly based on extramedullary hematopoiesis (myeloid metaplasia). For this reason, prodromal stages of (reticulin) fibrosis are overlooked by the clinicians. Up to 30% of patients with chronic myelogenous leukemia show a minimal to advanced MF that is significantly associated not only with corresponding clinical parameters but more importantly with prognosis. In polycythemia vera about 20% of patients may display some degree of reticulin fibrosis at diagnosis, depending on stage of the disease. Transformation into (collagen) MF after more than 10 years is accompanied by clinical signs of myeloid metaplasia (spent phase). Essential thrombocythemia (ET) is characterised by the absence of increased reticulin at onset and an insignificant progression into MF, provided diagnosis is performed by the WHO criteria. Discrimination of prefibrotic and early stages of chronic idiopathic myelofibrosis (CIMF) from ET is relevant, especially concerning the rate and time usually required for the development of MF with myeloid metaplasia (full-blown CIMF). In conclusion, more elaborate evaluations including standardized grading of MF is warranted by regarding bone marrow biopsy specimens in association with clinical parameters including follow-up examinations.

Bone marrow histopathology in the diagnosis of chronic myeloproliferative disorders: A forgotten pearl

Histopathology of bone marrow (BM) biopsies plays a crucial role in the interdisciplinary approach to diagnosis and classification of chronic myeloproliferative disorders (CMPDs). Based on careful clinicopathologic studies, BM features are critical determinants that help to predict overall prognosis, to detect complications such as progression to myelofibrosis and blast crisis, and to assess therapy-related changes. A systematic evaluation of BM histopathology allows an objective identification of cases of (true) essential thrombocythemia (ET) and their separation from (false) ET, which often is the prodromal stage of chronic idiopathic myelofibrosis (CIMF). By follow-up examinations that include BM biopsies, the progression of the disease process is unveiled, which is especially important for patients with initial (early) polycythemia vera and prefibrotic CIMF that may require a different therapeutic approach than the full-blown stages. In conclusion, BM biopsy should be considered as major diagnostic tool for evaluation and follow-up of patients enrolled in prospective studies.

A critical reappraisal of the WHO classification of the chronic myeloproliferative disorders

Following the introduction of the WHO classification of chronic myeloproliferative disorders (MPDs), after approximately 5 years, a critical reappraisal appears to be warranted. Retrospective clinico-pathological evaluations conducted in the meantime, as well as the detection of new biomarkers, may aid in testing the validity of these new criteria. Based on a large series of patients with chronic myeloid leukemia (CML), an analysis of bone marrow (BM) features and risk classifications revealed that the fiber content exerted a most important and independent impact on prognosis. This finding was also supported in a prospective randomized study and therefore myelofibrosis should be included in any staging system in CML related to survival. Moreover, it is important to emphasize the dynamics of the disease process in MPDs, especially in polycythemia vera (PV) and chronic idiopathic myelofibrosis (CIMF). Latent-stage PV is difficult to recognize when adhering to the proposed limits for hemoglobin (or red cell mass) without regarding the erythropoietin (EPO) level, endogenous erythroid colonies (EECs) or BM histopathology. Initial PV may firstly present with complications and, when accompanied by a high platelet count, mimics essential thrombocythemia (ET). Consequently, BM morphology and EPO level should be entered as major diagnostic criteria for PV. To document more accurately the progress of disease, a simplified scoring system concerning myelofibrosis has to be included in the histological description of CIMF. The diagnostic guidelines of BM features in ET should be improved because, usually, there is neither a significant proliferation nor left-shifting of the granulo- and erythropoiesis detectable and no relevant increase in reticulin. A comparison of clinical data and BM morphology reveals that biomarkers (EPO, EECs, PRV-1, JAK2) show an overlapping pattern of positivity between the different subtypes of MPDs.

Morphology of the bone marrow after stem cell transplantation

In many haematological conditions the only curative option is stem cell (SCT) or bone marrow (BM) transplantation. Little information exists about BM morphology following non-ablative engraftment. During the pretransplantation period and depending on the kind of pretreatment, there may be hypoplasia, residual disease and varying degrees of fibrosis. In the post-transplantation period, after 1-3 weeks of transfusion-dependent pancytopenia, the first signs of successful engraftment are indicated by the recurrence of neutrophils, monocytes and erythrocytes in the peripheral blood. In the BM there is slow regeneration of erythropoiesis, followed by the other lineages of haematopoiesis and increase in reticulin fibres or even a resolution of fibrosis. Diagnostic problems arise when neoplastic lympho- or haematopoiesis are maintained following transplantation. Moreover, there may be a significant graft versus tumour response reaction or an already relapsing disease needing aggressive treatment. On the other hand, a conspicuous dyshaematopoiesis should not be mistaken as representing a myelodysplastic syndrome. The presence of granulomas being treatment-related or a manifestation of intercurrent granulomatous disease has to be considered. More advanced knowledge of the histological features of regenerating BM will certainly aid the recognition of relapsing disease and is needed for the adequate reporting of post-transplant alterations associated with a successful or failing engraftment.

Trisomy 8 in prefibrotic early stages of chronic idiopathic myelofibrosis: a fluorescence in situ study of bone marrow biopsies

Repeatedly performed bone marrow biopsies were studied in 30 patients with chronic idiopathic myelofibrosis (CIMF) by fluorescence in situ hybridization to detect and quantify trisomy 8 anomaly during the evolution of disease. For the establishment of threshold values we used negative and positive control specimens. At least 500 cells were evaluated in each specimen and only nuclei with three distinctive signals were regarded as positive. According to the controls, 27 patients revealed false-positive signals ranging from 0 to 1.2% (0.88 +/- 1.12). On the other hand, 3 patients showed an incidence of more than 6.5% (up to 10.1%) in the initial prefibrotic as well as advanced fibro-osteosclerotic stages of CIMF. In conclusion, trisomy 8 has been demonstrated already in the prodromal stages of CIMF and therefore is not limited to classical fibro-osteosclerotic manifestations.

Grade of bone marrow fibrosis is associated with relevant hematological findings-a clinicopathological study on 865 patients with chronic idiopathic myelofibrosis

Controversy continues to exist regarding not only the exact definition and grading of myelofibrosis (MF), but also whether, and to what extent, this feature may be correlated with clinical findings. A retrospective study was performed involving 865 bone marrow (BM) biopsies together with the clinical records from patients with chronic idiopathic myelofibrosis (CIMF). Diagnosis was established according to the World Health Organization criteria, and assessment of MF followed a consensus scoring system that included four grades (MF-0 to MF-3). Histopathological and clinical evaluations were carried out in an independent fashion. Prefibrotic and early CIMF (MF-0/-1) were presented by 565 patients showing borderline to mild anemia and no or slight splenomegaly, but frequently, thrombocytosis exceeding 500x10(9)/l was shown. In 300 patients, manifest reticulin and collagen fibrosis (MF-2/-3) were characterized by marked anemia, gross splenomegaly, peripheral blasts, and normal to decreased platelet and leukocyte counts. The latter cohort was consistent with findings generally in keeping with MF with myeloid metaplasia. Regarding the stepwise evolution of disease, sequential BM examinations showed that in 103 patients, prefibrotic and early CIMF transformed into advanced stages accompanied by correspondingly developing clinical and histomorphological features. Survival analysis (univariate calculation) revealed a significantly more favorable prognosis in prefibrotic vs advanced stages of CIMF. On the other hand, higher classes of MF also exerted a higher clinical risk profile (Lille score). In conclusion, the dynamics of the disease process in CIMF are characterized by evolving MF in the BM and closely associated changes of relevant hematological findings.

Anagrelide does not exert a myelodysplastic effect on megakaryopoiesis: a comparative immunohistochemical and morphometric study with hydroxyurea

A comparative immunohistochemical and morphometric study was performed on megakaryocytes in 20 patients presenting with initial-early stage chronic idiopathic myelofibrosis and accompanying thrombocythemia to elucidate histological features developing after hydroxyurea (HU) versus anagrelide (ANA) therapy. Representative pre-and posttreatment bone marrow biopsies were involved including the monoclonal antibody CD61 for the identification of precursor and mature stages of megakaryopoiesis. An elaborate morphometric evaluation was in keeping with a left-shifting showing a more frequent occurrence of promegakaryoblasts and microforms in both therapy groups. However, contrasting ANA, HU generated defects of differentiation consistent with significant dysplastic changes. In conclusion, concern about a possible leukemogenic capacity following long-term HU therapy is supported by our findings.

[Secondary malignancies after successful primary treatment of malignant Hodgkin's lymphoma]

Malignant Hodgkin's lymphoma (HL) has become a curable disease through the increasing intensity of the treatment strategies applied. These regimens are aggressive, including radiotherapy and chemotherapy leading to the possibility of secondary malignancies. The German Hodgkin Lymphoma Study Group considered three cohorts including 5,411 patients with all stages of HL. In 127 patients a secondary solid tumor was diagnosed (cumulative risk 2%, median follow-up 72 months), with bronchial carcinomas (23.6%) and colorectal adenocarcinomas (20.5%) being the most frequent neoplasms. Secondary acute myeloid leukemia was found in 36 patients, another ten developed myeloid dysplasia (cumulative risk 1%, median follow-up 55 months). A total of 52 patients revealed a non-Hodgkin's lymphoma (NHL; cumulative risk 0.9%, median follow-up 46 months). The overall incidence of secondary malignancies was 3.9% in patients who had been treated successfully for their HL with radio- and/or chemotherapy.A secondary NHL can be particularly difficult to be distinguished from the preceding HL. Therefore, in case of a suspected relapse, a complete histopathological work-up must be performed.

Hematopathologic findings in chronic idiopathic myelofibrosis

Until now scant knowledge was available about the dynamics of chronic idiopathic myelofibrosis (CIMF). However, follow-up studies are in keeping with a stepwise evolution starting with a prefibrotic (hypercellular) phase that progressively transforms into the classical fibro-osteosclerotic endstage with myeloid metaplasia. Prefibrotic CIMF is characterized by a granulocytic and megakaryocytic myeloproliferation lacking an increase in reticulin. Most conspicuous are abnormalities of megakaryopoiesis with regard to their histotopography and maturation. There is a more than 65% probability of progression from an early to advanced CIMF accompanied by increasing anemia, splenomegaly, and leuko-erythroblastosis. A significant relationship is recognizable among frequency, tortuosity, and luminal dilation of the microvessels and the extent of myelofibrosis. Quantity of CD34(+) progenitor cells in the bone marrow (BM) reveals a close association with advancement of disease (fibrosis, splenomegaly, anemia, peripheral blasts) and therefore prognosis. Cell kinetic studies show increased proliferation associated with a higher rate of apoptosis in initial (hypercellular) stages, as well as a reduced endoreduplicative activity of megakaryopoiesis and a blocked synthesis phase of the erythroid precursors. It is noteworthy that prefibrotic and early CIMF often present with a marked thrombocytosis mimicking essential thrombocythemia. Regarding prognosis, early CIMF is associated with a significantly more favorable survival than advanced stages.

Pegylated interferon for the treatment of high risk essential thrombocythemia: results of a phase II study

BACKGROUND AND OBJECTIVES

Patients with high-risk essential thrombocythemia require cytoreductive therapy in order to normalize the elevated platelet counts. We evaluated the efficacy and toxicity of pegylated interferon in high-risk essential thrombocythemia in a phase II trial.

DESIGN AND METHODS

Thirty-six patients with high-risk essential thrombocythemia (median age 54 years; range, 24-72 years) were studied. The dose of pegylated interferon was initially 50 mg per week and could be escalated up to 150 mg per week.

RESULTS

During the first three months platelet counts decreased significantly from a median baseline count of 895x10(9)/L (range: 383-1779) to a median count of 485x10(9)/L (range: 211-1283; p<=0.001). A complete response was defined as platelet counts < 450x10(9)/L. The complete response rate was 39%, 47%, 58% and 67% at 3, 6, 9 and 12 months of treatment, respectively. There were 25%, 11%, 8% and 0% poor responders, defined as patients with platelet counts > 600x10(9)/L, at 3, 6, 9 and 12 months of treatment, respectively. After a median time of 23 months (range 3-39 months) 23 of 36 patients (64%) are still receiving pegylated interferon. In ten patients (28%) treatment was stopped due to grade 1 to 2 toxicity, classified according to the WHO standard toxicity scale. One patient, who responded partially to pegylated interferon (platelet count 542x10(9)/L), had a cerebral stroke after 23 months of treatment.

INTERPRETATION AND CONCLUSIONS

In high-risk essential thrombocythemia sustained treatment with pegylated interferon is effective and safe in reducing platelet counts with a toxicity comparable to that of conventional interferon.

Dynamics of bone marrow changes in patients with chronic idiopathic myelofibrosis following allogeneic stem cell transplantation

Scant knowledge exists about the dynamics of fibro-osteosclerotic bone marrow (BM) lesions and regeneration of hematopoiesis following allogeneic peripheral stem cell transplantation (SCT) in chronic idiopathic myelofibrosis. Therefore, an immunohistochemical and morphometric study was performed on BM biopsies in 20 patients before and at standardized intervals (days 30 through 384) following SCT. In responding patients, a total regression of the pretransplant increased fibrosis was completed in the posttransplant period after about six months, while the extent of osteosclerosis did not change significantly during observation time. The quantity of CD61+ megakaryocytes including precursors was strikingly variable after SCT and, by using planimetric methods, atypical microforms exhibiting a dysplastic aspect could be demonstrated. These anomalies may be responsible for posttransplant thrombocytopenia. CD34+ progenitor cells were increased before transplantation, however, their number declined rapidly to normal values in responding patients. Nucleated erythroid precursors revealed a decreased amount before and after SCT accounting for anemia. Large clusters of this cell lineage indicated an initial hematopoietic reconstitution comparable with the expansion of the neutrophil granulopoiesis. Proliferative activity and apoptosis showed an increase until one year after SCT that implied a still regenerating hematopoiesis in keeping with an enhanced cell turnover.

Standardization of bone marrow features--does it work in hematopathology for histological discrimination of different disease patterns?

Standardized bone marrow (BM) features determined by semiquantitative scoring are valuable tools for the recognition and easily reproducible interpretation of histological patterns in hematopathology. This procedure may help to characterize various disease entities, but especially to differentiate chronic myeloproliferative disorders (MPDs) with increased platelet counts from reactive thrombocytosis (RTh). A clear-cut separation of these conditions continues to present a major problem in hematology. Therefore MPDs are a most suitable model to test the diagnostic relevance of this procedure. By regarding the literature and based on archive material that involved BM biopsies of 319 patients, a semiquantitative grading of histological parameters was performed. Standardized features were applied for a stepwise discriminant analysis to establish different sets of variables exerting a diagnostic impact. A distinction into five histological patterns was achieved that showed a correctly predicted group membership of about 94 %. These were consistent with the clinicopathological diagnosis of polycythemia vera, essential thrombocythemia (ET), prefibrotic or early fibrotic chronic idiopathic myelofibrosis (CIMF) and finally RTh. Variables of discriminating potency according to their ranking included megakaryopoiesis (maturation defects, nuclear lobulation, naked and bulbous nuclei, small and giant size), reticulin fibers, erythro- and granulopoiesis (left shifting and quantity) and cellularity. These findings are in keeping with the assumption that characteristic patterns of BM histopathology can be assigned to different subtypes of MDPs mimicking ET. Discrimination between ET and especially early stage CIMF with thrombocythemia is warranted because of significant implications concerning therapeutic strategies, follow-up examinations and survival. Regarding these results, a schematic procedure is proposed to be used for daily routine diagnosis concerning the discrimination of MPDs.

Bone marrow changes in chronic myelogenous leukaemia after long-term treatment with the tyrosine kinase inhibitor STI571: an immunohistochemical study on 75 patients

AIMS

To carry out an immunohistochemical study on bone marrow (BM) biopsy specimens in 75 patients with chronic myelogenous leukaemia (CML) on long-term STI571 therapy.

METHODS AND RESULTS

Sequential BM specimens taken at intervals of 21 +/- 6 months were investigated by enzyme- and immunohistochemistry including proliferating cell nuclear antigen and apoptosis. Evaluation was performed either by semiquantitative scoring or by morphometry (CD61+ megakaryopoiesis). In 41 patients with chronic phase CML, treatment resulted in a significant decrease in cellularity and neutrophil granulopoiesis contrasting with an accumulation of erythroid precursor cells. Morphometry showed a reduction of abnormal micromegakaryocytes consistent with normalization. Regression of myelofibrosis was identified in eight of 15 patients, whereas progression occurred in 17 patients; mostly in those with acceleration and blastic crisis. The increased post-treatment incidence of reactive lymphoid nodules was remarkable. Myeloblasts, CD34+ progenitors and immature myelomonocytic cells initially decreased, but recurred in 14 patients who later developed a relapse. STI571 exerted an inhibitory effect on cell proliferation associated with enhanced apoptosis in responding patients.

CONCLUSION

Long-term treatment with STI571 exerts pronounced changes on BM histopathology that not only involve haematopoiesis and stromal constituents, but also proliferation and apoptosis.

Diagnostic impact of bone marrow histopathology in polycythemia vera (PV)

The criteria of the Polycythemia Vera Study Group (PVSG), although acknowledged as the gold standard to establish the diagnosis of polycythemia vera (PV), do not regard bone marrow (BM) histopathology. Arguments include the existence of sufficient objective markers of disease and the lack of independently performed morphological studies or standardized criteria. The aim of this review is to evaluate morphological characteristics of erythrocytosis and to determine whether distinctive patterns of histopathology exist. A review of the pertinent literature and evaluation of 334 patients from our files with a borderline to marked increase in hemoglobin was performed. In extension to former descriptions of BM features by the PVSG, a tri-lineage myeloproliferation (panmyelosis) with a pleomorphous appearance of megakaryopoiesis revealed that, besides increase in size, there was a lack of gross cytological anomalies. Differentiation from secondary polycythemia (SP) was accomplished by regarding these features and the conspicuously expressed stromal changes (plasmacytosis, eosinophils, cell debris and iron deposits). In about 96% of this cohort a clear-cut separation from SP was achieved, even in the initial (latent) stages. When accompanied by an elevated platelet count, these precursor stages may clinically mimick essential thrombocythemia because they are not recognized by the conventional criteria. Advanced stages (spent phases) of PV were consistent with an increased left-shifted granulocytic proliferation, accompanied by reduction of erythroid precursors and progressive myelofibrosis (post-polycythemic myeloid metaplasia). Finally, an increase in dysplastic changes and immaturity signalled a transition into blastic crisis. In conclusion, PV is characterized by a distinctive pattern of histopathology that has been gained in an independent and blind fashion and therefore, dissolves arguments about failing specificity.

Bone marrow angiogenesis: methods of quantification and changes evolving in chronic myeloproliferative disorders

Until now little information is available about bone marrow (BM) angiogenesis in chronic myeloproliferative disorders (CMPDs). Amongst the various immunohistochemical markers for endothelial cells CD34 and CD105 have proven to be most reliable since they exhibit no relevant co-staining. Determination of vascularity has to include pathophysiological aspects of perfusion. Therefore, quantification of the microvascular density (MVD) by the so-called hot spot method has to be improved by parameters that characterize blood flow more properly like microvessel area (luminal distension), shape (form factor), tortuosity, and branching (maximal vessel length). In comparison to the normal BM chronic myeloid leukemia (CML) revealed a significant increase in MVD which was functionally associated with elevated levels of angiogenic cytokines. Structure of vessels was significantly altered by showing an enhanced irregularity of shape and tortuosity and increase in fibers was conspicuously accompanied by a higher degree of MVD. Contrasting the group of patients with Imatinib (STI571) therapy interferon failed to reduce the number of vessels. Following bone marrow transplantation a significant enhancement of the MVD was found in the early post-transplant period, but after about 6 months normalization occurred. Anomalies of microvascular architecture were easily demonstrable by three-dimensional reconstruction and consisted of a complex branching network of irregular shaped sinuses. Chronic idiopathic myelofibrosis displayed a significant increase in the MVD only in the advanced fibrosclerotic stages. This feature was accompanied by an enhanced luminal distension and tortuosity, thus contrasting the prefibrotic and early fibrotic phases of this disorder. Similar to CML a relationship between evolving myelofibrosis and change in vascular architecture was encountered. This feature may present a possible target for future anti-angiogenic therapy. In essential thrombocythemia there is only a mild increase in MVD detectable while in polycythemia vera besides an enlarged number, a luminal dilation due to the densely packed erythrocytes is recognizable. In conclusion, contrasting the usually applied quantification technique more elaborate morphometrical methods are warranted to obtain a better insight into the vascular architecture of the BM. In CMPDs angiogenesis is significantly associated with the evolution of myelofibrosis and may be altered by therapeutic regimens probably due to changes in cytokine release.

Regression der Philadelphia-Chromosom (bcr/abl)-positiven Myelo- und Megakaryopoiese unter Imatinib(STI571)-Therapie bei chronischer myeloischer Leuk�mie (CML)

In chronic myeloid leukemia following therapy with Imatinib (STI571) hematologic and cytogenetic response is associated with conspicuous changes of bone marrow morphology. However, it is not known to which extent these alterations are accompanied by a loss of the bcr/abl translocation. To study regression of the leukemic cell population we recruited 14 patients lacking pretreatment. Therapy resulted in a reduction of CD61(+) megakaryopoiesis. Dwarf megakaryocytes characteristic for this disorder were replaced by large, normally appearing cells of this lineage. Morphometric analysis confirmed the significant decrease in the number of micromegakaryocytes and yielded planimetric parameters in keeping with normalization. Moreover, a fluorescence in-situ hybridization study in five patients of this cohort revealed that before therapy 70% of all myeloid cells exhibited the bcr/abl gene. Regarding megakaryopoiesis about 65% of the micromegakaryocytes displayed positive signals. Following treatment these bcr/abl(+) cell populations decreased significantly while the emerging large megakaryocytes lacked a proper labeling. Because cytogenetic response and reduction of atypical micromegakaryocytes are linked, this feature may be useful to monitor therapeutic efficacy.

Effects of the tyrosine kinase inhibitor imatinib mesylate (STI571) on bone marrow features in patients with chronic myelogenous leukemia

Preliminary data are available about bone marrow (BM) changes in patients with chronic myeloid leukemia (CML) who received the molecularly targeted and highly effective tyrosine kinase inhibitor Imatinib mesylate (STI571). This review is focused on a systematic assessment of BM features detectable at different stages of CML (stable, accelerated, blastic) following long-term (more than 10 months) treatment. By applying enzyme- and immunohistochemistry including monoclonal antibodies visualizing proliferating cell nuclear antigen (PCNA) and apoptosis (anti-apostatin), a more elaborate insight into alterations affecting hematopoiesis and the stroma compartment was gained. In patients with stable-phase CML therapy resulted in a significant reduction in cellularity, neutrophil granulopoiesis and number of megakaryocytes, accompanied by a retrieval of erythroid precursors. In patients with Imatinib as the only treatment morphometric analysis of CD61+ megakaryopoiesis was in keeping with a significant decrease in maturation defects implying a lesser amount of atypical micromegakaryocytes almost consistent with normalization. Moreover, a reduction of the initially enhanced (CD34+) microvessel density was detectable associated with a decrease in luminal distension. Regression of marked to moderate myelofibrosis was recognizable in about 70% of patients especially in the accelerated and blastic phases. The amount of myeloblasts, CD34+ progenitor cells and lysozyme-expressing immature myelomonocytic cells declined with treatment, but recurred in about 19% of patients that developed a leukemic relapse after 21+/-6 months of therapy. Data on proliferative activity and apoptosis in general supported in vitro findings concerning the inhibitory effect of this agent on growth associated with a tendency for stimulated apoptosis, at least in responding patients.

Regeneration of heart muscle tissue: quantification of chimeric cardiomyocytes and endothelial cells following transplantation

Persuasive evidence has been recently provided that adult bone marrow (BM) cells exert greater plasticity than previously assumed. This review is focused on the quantification of mixed chimerism (mCh) in the hearts (cardiomyocytes and endothelial cells) of patients after orthotopic heart to heart transplantation (HHT) in comparison to full (unmanipulated) allogeneic BM and peripheral blood stem cell (PBSC) transplants. Following a sex-mismatched transplantation constellation heart muscle tissue obtained at autopsy was examined. Evaluation of mCh was most often performed by immunophenotyping combined with fluorescence in-situ hybridization (FISH) applying x- and y-chromosome-specific DNA probes. When comparing our data with the results of former studies that were regularly based on the detection of the y-chromosome alone, the quantity of chimeric cardiomyocytes after HHT ranged from 0% to 9%. On the other hand, after full BM transplantats (chimeric) cardiomyocytes of donor-type origin appeared at an incidence between 0.23% to 6.4%. These disturbing inconsistencies were assumed to be related to methodology: the restriction to the y-chromosome, disregard of the plane of section (detection sensitivity ranging between 35% and 67%) and state of tissue preservation (cadaver hearts). Therefore, when strictly applying dual color FISH and limiting the recognition of chimeric cardiomyocytes and endothelial cells to the presence of two distinctive signals detection sensitivity was significantly enhanced. Contrasting a total congruence with the genotyping in control specimens of normal cadaver hearts, a striking disparity in the extent of mCh was found depending on the different modes of transplantation. After allografting with PBSC a considerably low incidence (1.6%) of chimeric cardiomyocytes was determined contrasting with 5.3% of donor-derived cells after full BM transplants. Following HHT host-type endothelial cells (16.2%) of the intramural and subepicardial vessel walls were more often encountered than following BM and PBSC allografting. These findings are in keeping with the assumption of a sprouting and migration of vascular structures into the donor heart from the site of surgical aligment and injury between retained host and donor atrial walls. When considering the other methods of transplantation (BM, PBSC) the data on chimeric endothelial cells support the hypothesis of a common hemangioblast. Concerning the cardiomyocytes it seems most reasonable to assume that primitive mesenchymal stem cells of the BM play a pivotal role in the development of mCh. This phenomenon is more extensively expressed than previously expected and may be related to an enforced repair of the damaged myocardium during the post-transplant period as the sequel of myeloablative (cardiotoxic) conditioning.

Acute panmyelosis with myelofibrosis

Acute panmyelosis with myelofibrosis (APMF) is an ill-defined disorder that may either evolve as a clonal hematopoietic condition or as a sequel of toxic exposure to the bone marrow (BM). Therefore, controversy and discussion continues as to whether APMF may be considered as a hyperfibrotic (de novo) myelodysplastic syndrome (MDS), as acute myeloid leukemia (AML) or as a severe toxic myelopathy with accompanying myelofibrosis. In this context scant knowledge exists about BM findings, but especially evolution of this disorder according to sequential examinations. Clinically patients present with pancytopenia, a very few blasts in the peripheral blood and no or little splenomegaly. Initially BM histopathology is characterized by different degrees of reticulin-collagen fibrosis and wide ranges of cellularity with a prominent left-shifted and often macrocytic erythropoiesis associated with a reduction and maturation defects of the neutrophil series. Most conspicuous are abnormalities of the megakaryocytes including loose clustering, dislocation towards the endosteal border and appearance of atypical microforms with compact nuclei. Moreover, besides myelofibrosis in a number of patients the interstitial compartment displays a remarkable inflammatory reaction with lymphoid nodules, abundant iron-laden macrophages, perivascular plasmacytosis and increase in microvessels. Repeatedly performed BM biopsies reveal an accumulation of dispersed or clustered CD34+ and lysozyme-expressing blasts in keeping with the insidious transformation into acute leukemia. Prognosis is unfavorable with a median survival of less than 1 year. In conclusion, APMF has to be regarded as a condition that shows considerable overlappings with primary hyperfibrotic MDS, AML and toxic myelopathy (secondary MDS) with accompanying myelofibrosis and therefore can not be considered as a definite clinical entity.

Acute panmyelosis with myelofibrosis: a clinicopathological study on 46 patients including histochemistry of bone marrow biopsies and follow-up

Controversy continues whether acute panmyelosis with myelofibrosis (APMF) exists as a well-defined clinicopathological entity. Following exclusion of overt acute myeloid leukemia (AML), especially the megakaryoblastic subtype, a retrospective study was performed on 46 patients with clinical and morphological features suggesting the diagnosis of APMF. All patients had a bone marrow (BM) biopsy performed at onset, and 13 had follow-up examinations. Enzyme histochemical and immunohistochemical techniques were applied and BM features evaluated by a semiquantitative scoring system. Clinical findings consisted of pancytopenia associated with a left-shifted differential count of the peripheral blood (less than 5% blasts) and no or minor splenomegaly. During follow-up (median survival 9 months) 35 patients developed severe BM insufficiency and 10 transformed into overt AML. Although myelofibrosis was a characteristic finding, other BM features proved to be heterogeneous. Cellularity was reduced in 13 and increased in 25 specimens. Most prominent was a left-shifted, often macrocytic erythropoiesis and a maturation defect of the neutrophil series. In 15 patients an increase (less than 20%) in CD34+ progenitors, immature myelomonocytic cells, and megakaryoblasts was noted. Abnormalities of megakaryocytes (atypical microforms, clustering, dysplasia) were regularly present. The stroma showed an inflammatory reaction (perivascular plasmacytosis, lymphoid nodules, many macrophages, iron deposits) in about 50% of the samples. Sequential BM biopsies revealed an accumulation of lysozyme-expressing myelomonocytic and CD34+ progenitor cells suggesting an increase in blasts. In conclusion, APMF may not be a distinct entity, but includes hyperfibrotic myelodysplastic syndromes (MDS) either primary or secondary, a rare form of initial AML with fibrosis, and even cases of toxic myelopathy.

Prefibrotic chronic idiopathic myelofibrosis--a diagnostic enigma?

To analyze precursor lesions of chronic idiopathic myelofibrosis (CIMF) 21 patients were recruited who developed manifest myelofibrosis after about 70 months, preceded by a prefibrotic stage but without interference by cytoreductive therapy. Prodromal bone marrow lesions included a prominent granulocytic and megakaryocytic proliferation with megakaryocytes showing conspicuous abnormalities associated with a borderline to slight anemia, thrombocytosis, and minimal splenomegaly. Comparison of this cohort with 211 additional patients at this precursor stage revealed no differences concerning clinical findings and bone marrow histopathology. Relative incidence of prefibrotic CIMF was 24% and median survival 143 months, thus contrasting overt CIMF (82 months). In CIMF progressive myelofibrosis occurred in more than 50% of patients according to the last biopsy specimen; however, this figure increased according to relevant clinical data in the follow-up period.

[Therapy-related changes of angiogenesis in Philadelphia chromosome positive chronic myelogenous leukemia]

To elucidate the effect of first-line treatment with interferon (IFN), hydroxyurea (HU) and the tyrosine kinase inhibitor imatinib (STI571) on angiogenesis, we studied bone marrow (BM) biopsies in 104 patients with chronic myelogenous leukemia (CML) and 138 patients before and after allogeneic BM transplantation (BMT). After immunostaining (CD34) and morphometric analysis in comparison with a control group, CML specimens showed an increased vascularity and conspicuous morphological abnormalities of microvessels. A close relationship between microvessels and fiber density was detectable in initial biopsies and also in repeatedly performed examinations following therapy. Monotherapy by imatinib and HU generated a significant reduction of microvessels and reticulin fibers in contrast to changes after IFN administration or combination regimens of IFN and HU. A persistence of numerical and structural anomalies of vasculature was observable even several months after BMT. These anomalies shed some light on disturbances of the stroma compartment after myeloablative therapy. The relationship between BM vascularity and fibers is probably dependent on concomitant changes of megakaryopoiesis as the source of various mediators involved in the development of myelofibrosis and neo-angiogenesis acting within a complex functional network.

Therapy-related changes of the bone marrow in chronic idiopathic myelofibrosis

In chronic myeloproliferative disorders (CMPDs) a conflict of opinion exists regarding therapy-induced bone marrow (BM) changes and the evolution of myelofibrosis during the lengthy course of the disease. For a more elaborate study of these features chronic idiopathic myelofibrosis (IMF) seems to be a most suitable condition. Therefore this review is focused on this CMPD and amongst other findings analyzes data from a series of 340 patients with a long follow-up including 893 biopsies (median interval of 32 months). The ensuing results were compared with those communicated in the relevant literature. In addition to a control group of 153 patients with IMF who received only symptomatic treatment, therapy groups included busulfan, hydroxyurea, interferon and various combinations. In all groups hypoplasia of a varying degree was a frequent finding (6%) and often accompanied by a patchy arrangement of hematopoiesis. Most conspicuous was a gelatinous edema showing a tendency to develop a discrete reticulin fibrosis (scleredema). Aplasia developed in 7.7% of patients, usually at terminal stages of the disease independently of treatment. Minimal to moderate maturation defects of hematopoiesis involved especially megakaryocytes and erythroid precursors, but overt myelodysplastic features were most prominent following hydroxyurea and busulfan therapy. Acceleration and blastic crisis were characterized not only by increasing dysplastic changes, but also by the appearance of blasts including CD34+ cells. Semiquantitative grading of the fiber content revealed that 183 patients (54%) without or with moderate fibrosis at the beginning showed a significant progression and therefore contrasted with the 66 patients with a stable state. Following this calculation no relevant differences in the evolution of myelofibrosis were evident in the various therapy groups especially not following interferon treatment. In a few patients a regression was found which was accompanied by a severe hypoplasia or aplasia compatible with a myelo-ablative effect. In conclusion, peculiar BM changes, in particular conspicuously expressed myelodysplastic features are consistent with therapy-related lesions. Development of myelofibrosis in IMF is obviously due to disease progression unrelated to stage at diagnosis and not significantly influenced by treatment modalities.

Bone marrow histopathology following cytoreductive therapy in chronic idiopathic myelofibrosis

AIMS

To analyse systematically therapy-induced lesions of haematopoiesis in chronic idiopathic myelofibrosis (IMF).

METHODS AND RESULTS

A total of 759 sequential bone marrow (BM) biopsies (median interval 32 months) were performed in 261 patients with IMF. Besides a control group (symptomatic treatment), monotherapies included busulfan, hydroxyurea and interferon. In all therapy groups hypoplasia of varying degree was a frequent finding and often accompanied by a patchy distribution of haematopoiesis. Most conspicuous was gelatinous oedema showing a tendency to develop discrete reticulin fibrosis (scleroedema). Minimal to moderate maturation defects of megakaryopoiesis and erythroid precursors occurred, but overt myelodysplastic features were most prominent following hydroxyurea and busulfan therapy. Acceleration and blastic crisis were characterized by the appearance of immature and CD34+ progenitor cells. Concerning the dynamics of fibrosis, no differences were observed between controls and the various therapy groups. In 143 patients (55%) without or with little reticulin at onset, an increase in myelofibrosis was detectable that progressed to overt collagen fibrosis.

CONCLUSIONS

Therapy-related bone marrow lesions in IMF comprise a strikingly variable spectrum that may include aplasia with scleroedema and a patchy distribution of myelodysplastic haematopoiesis associated with progressive myelofibrosis.

Mixed chimerism of erythro- and megakaryopoiesis following allogeneic bone marrow transplantation

Until now, studies on mixed chimerism (MCh) after allogeneic bone marrow transplantation (BMT) have predominantly focused on the B- and T-lymphocyte population, but not on distinct myeloid cell lineages like nucleated erythroid precursors and megakaryocytes. To evaluate the lineage-restricted MCh more explicitly in 10 patients with chronic myelogenous leukemia (CML), a quantitative analysis was performed on bone marrow biopsies following a sex-mismatched host/donor constellation. Techniques included immunophenotyping (antiglycophorin C, CD61) for the identification of erythro- and megakaryopoiesis and a simultaneously conducted genotyping with x- and y-chromosome-specific DNA probes. Normal bone marrow and specimens taken before BMT served as controls. Contrasting a total gender-dependent sex-typing in the latter samples in the early and late posttransplant period (up to 586 days), 3-9% erythroid precursors and about 16% megakaryocytes revealed a host-type origin. This significantly higher number of host megakaryocytes is explained by their polyploidy generating an increased probability to detect positive signals at a certain section level of the corresponding biopsies. A striking conversion of MCh to a recipient cell type was found in leukemic relapse with a more than 90% host-derived erythroid and megakaryocytic cell population in 4 patients approximately 643 days after BMT.

Dynamics of fibrosis in chronic idiopathic (primary) myelofibrosis during therapy: a follow-up study on 309 patients

Controversial issues in chronic idiopathic myelofibrosis (IMP) are amongst others the evolution of the disease process and the influence of therapy on the dynamics of fibrosis. For this reason, a multicenter observational study was performed on 309 patients with IMF that had a long follow-up including 822 bone marrow biopsies at a median interval of 32 months. In addition to a control group (156 patients) with symptomatic treatment, monotherapy consisted of busulfan (30 patients), hydroxyurea (52 patients), interferon (26 patients) and various combinations (48 patients). Density and quality (reticulin/collagen) of fibers was determined by a semiquantitative scoring system. Independent of therapeutic regimens at the time of the last bone marrow biopsy 67% of the patients with grades 0-2 fibrosis revealed a progression, 42% stable state and 6% regression of myelofibrosis. Because of significant differences concerning frequencies of biopsies and endpoints of examinations, individual changes in the grades of fibrosis were evaluated with regard to treatment applied at standardized intervals of 20 months. According to this calculation no relevant differences in the dynamics of myelofibrosis (progression, stable state) was detectable in the control group compared to the other therapeutic modalities. The few patients with a regression of myelofibrosis usually presented with severe hypoplasia compatible with a myelo-ablative effect by aggressive chemotherapy. In conclusion, persuasive evidence has been produced that myelofibrosis in IMF is characterized by a stepwise progression and that this process is not significantly influenced by current treatment strategies.

Dynamics of lineage-restricted mixed chimerism following sex-mismatched allogeneic bone marrow transplantation

Scant knowledge is available about the dynamics of lineage-specific mixed chimerism (Ch) following bone marrow transplantation (BMT). This review is focused on findings derived from bone marrow (BM) biopsies in patients with chronic myeloid leukemia (CML) including a sex-mismatched host/donor constellation. Appropriate techniques involved immunophenotyping by monoclonal antibodies to identify the various cell lineages, dual color fluorescence in situ hybridization (FISH) with x- and y-chromosome-specific DNA-probes and a proper detection system for a simultaneous labeling of the bcr/abl locus. A significant degree of Ch with more than 20% host CD34+ progenitors was found in the early and late (up to 200 days after BMT) posttransplant period. However, only 10% of these cells harbored the bcr/abl translocation gene. This result fits well with corresponding molecular biological findings of so-called minimal residual disease. Conversion of Ch evolved during leukemic relapse with 90% host progenitors of which 50% revealed the bcr/abl locus. A Ch of nucleated erythroid percursors (5%) and CD68+ macrophages (8%) was expressed to a significantly lower degree. The slightly increased frequency found in CD61+ megakaryocytes (16%) was probably due to the polyploid state of these cells. Similar to the CD34+ progenitor cells abrupt changes from donor to host type was associated with an insidious transformation into recurrent leukemia. The CD34+ endothelial cells showed a minor degree of Ch, because donor-derived elements ranged from 18% to 25%. Leukemic relapse was characterized by an almost complete conversion of the endothelial cells to a host type. These findings point towards a CD34+ progenitor cell origin of the (leukemic) endothelial cell layer and suggests that their dysfunction may contribute to an expansion of the neoplastic clone.

Chronic myeloproliferative disorders with thrombocythemia: a comparative study of two classification systems (PVSG, WHO) on 839 patients

A multicenter observational study was performed on 839 adult patients with a chronic myeloproliferative disorder and a platelet count in excess of 600 x 10(9)/l to compare the updated criteria of the Polycythemia Vera Study Group (PVSG) with the recently published WHO classification. Essential thrombocythemia (ET) was diagnosed in 483 patients according to the PVSG; however, when considering histopathology as a major diagnostic feature of the WHO criteria, (true) ET could be established in only 162 patients. The remaining cases were found to represent either initially prefibrotic (184 patients) or early fibrotic (137 patients) chronic idiopathic myelofibrosis (IMF). On the other hand, both classification systems enabled a clear-cut distinction of patients showing overt IMF and polycythemia vera. Follow-up examinations in 140 patients with ET according to the PVSG criteria included also sequential bone marrow biopsies (interval: 38+/-30 months). A transition into mild reticulin fibrosis occurred in only 2 of 49 patients with (true) ET in contrast to 45 of 91 patients with initial and early IMF where a progression into overt myelofibrosis was encountered. Survival patterns for ET displayed significant differences because according to the PVSG a 16.5% disease-specific loss of life expectancy was calculable compared to a value of only 8.9% when following the WHO criteria. Contrasting this finding, initial and early IMF mimicking ET was characteriZed by a reduction of life expectancy ranging between 21.6% and 32.3 %. In conclusion, a more accurate classification of ET is warranted by regarding the WHO criteria that include histopathology as a major feature for diagnosis.

Mixed chimerism of bone marrow vessels (endothelial cells, myofibroblasts) following allogeneic transplantation for chronic myelogenous leukemia

Experimental findings support the hypothesis that within the functional network of the bone marrow (BM) microenvironment the endothelial cells (ECs) exert a pivotal role as gatekeepers by controlling the trafficking and homing of progenitor cells. However, little information is available concerning the origin of ECs after allogeneic bone marrow transplantation (BMT) in CML. To determine the extent of mixed chimerism (MCh) a simultaneous immunohistochemical and fluorescence in-situ hybridization (FISH) study was performed on BM biopsies derived from patients following sex-mismatched BMT with full unmanipulated BM. ECs were identified by their staining with CD34 and the myofibroblasts (MFs) of large vessels were labeled by an antibody against alpha-smooth muscle actin. For sex-typing and demonstration of the bcr/abl fusion product appropriate commercially available probes and detection systems were applied. Contrasting a total congruence of labeling in control samples five patients showed donor type ECs in the early posttransplant period in about 20%. In the remaining four patients the amount of donor type ECs increased slightly after the third month up to 30%. A total of 26 MFs could be identified lining large capillaries and arterioles that exclusively revealed a host origin. Following successful engraftment only very few of the persistent host-derived ECs also displayed the bcr/abl gene. In five patients, a conversion of MCh from donor to host type ECs was recognizable during the evolution of leukemic relapse. This finding was accompanied by a bcr/abl rearrangement of about 10% of these cells. In conclusion, following myelo-ablative therapy, a survival of a considerable number of ECs and MFs of the vessel walls has been found implying persistence of host-derived vascular structures of the BM stroma. However, in only a small proportion bcr/abl+ ECs and thus minimal residual disease was detectable. Evolution of leukemic relapse was characterized by conversion of MCh with almost total loss of donor type ECs and increase in number of bcr/abl+ ECs.

Diagnostic differentiation of essential thrombocythaemia from thrombocythaemias associated with chronic idiopathic myelofibrosis by discriminate analysis of bone marrow features--a clinicopathological study on 272 patients

Until now diagnosis of essential thrombocythaemia (ET) is generally performed by following the criteria of the Polycythaemia Vera Study Group (PVSG) that only marginally regards morphological features. Bone marrow biopsies were studied from 272 patients with ET in strict accordance with the PVSG guidelines and also from 35 control patients with reactive thrombocytosis. To define morphological features of distinctive impact more accurately, we performed a stepwise discriminant analysis of 16 morphological parameters based on histochemical staining reactions and semiquantitative grading of standardized features. A clear-cut separation into three distinctive histological patterns was accomplished that showed in more than 96% a correct predicted classification. Variables of significant impact included fibre content, quantity and cytological abnormalities of megakaryopoiesis like bulbous (cloud-like) nuclei, degree of nuclear lobulation and presence of giant forms. These changes were not detectable in the control group. The different constellations of histopathological features could be assigned to true ET (98 patients) and false ET, i.e. 136 patients with prefibrotic and 38 patients with early fibrotic chronic idiopathic myelofibrosis (IMF) accompanied by thrombocythaemia. A re-evaluation of clinical findings was in keeping with this classification into three categories that exerted significant differences to develop myelofibrosis during observation time and also different survival patterns. Contrasting IMF true ET is characterized by a pronounced proliferation of the megakaryocyte lineage showing large to giant cells without maturation defects and no relevant increase in reticulin fibres. Discrimination between these entities is warranted, because of a significant difference in presenting haematological data, follow-up and life expectancy.

[Quantification and morphometric analysis of vascular structures in the bone marrow. A critical review]

The important role of angiogenesis for invasion, tumor growth, metastasis and progression of solid tumors is well established. Only recently, the clinical significance of neovascularization in hematological neoplasms has come into the focus of scientific efforts. Emerging data from these studies suggest that the vascular architecture exerts a pivotal role in acute leukemias and multiple myeloma as well as myeloproliferative disorders. Thus, angiogenesis seems to maintain a general condition for malignant growth and the progression of hematological diseases. However, a major shortcoming is that most of the previous studies include only a simple quantitative evaluation of the microvessel density, and applied methods which were developed primarily for the characterization of angiogenesis in solid tumors. In this context it should not be overlooked that solid neoplasms and the bone marrow reveal significant differences regarding the vascular structures and the distribution of microvessels. Therefore, the usually applied, so-called hot-spot techniques, should be amended by an appropriate and more elaborate computer-assisted morphometric analysis of the microvessel structures. This additional spectrum of information regarding quantity and quality of angiogenesis, enables a further understanding of the morphological changes in the course of diseases, and in particular the effect of various therapies on bone marrow vascularization.

[Differentiation of granulomatous lesions in the bone marrow]

Granulomas are an infrequent finding in bone marrow biopsies and may be associated with a broad spectrum of infectious and non-infectious disorders. In this context sarcoidosis generally reveals the highest incidence of such bone marrow lesions. Other granulomas may be encountered in drug-induced secondary changes (toxic myelopathy) and in particular also in HIV myelopathy. In these cases the granulomas are small, ill-defined and difficult to recognize. Special staining methods are required to detect microorganisms. Fibrin ring granulomas (doughnut granulomas) are typical for Q-fever, but may also be seen in reactive conditions, after drug therapy and in the course of other infectious disorders, such as Lyme disease. Therefore a broad serological testing should be performed. In conclusion, in most cases the morphological findings in the bone marrow are not specific so that a synoptical approach regarding histological, clinical and serological data is warranted to reach the correct diagnosis.

[Extramedullary initial manifestations of acute myeloid leukemia (AML)]

Extramedullary myeloblastic tumors, so-called myelosarcomas (granulocytic sarcomas, chloromas) have been reported only sporadically in the pertinent literature which reflects their rather infrequent occurrence. These lesions may accompany the initial manifestation or signal relapse of acute myeloid leukemia (AML) or coincide with blastic transformation of a chronic myeloproliferative disorder. However, even more rarely, primary myelosarcomas may precede AML by months or years or may be associated with myelodysplastic syndromes (MDS) that never progress to manifest leukemia. In a retrospective evaluation a clinicopathological study on these latter two variants of isolated extramedullary manifestations of AML was performed to elucidate certain aspects of site involvement and histopathology by application of enzyme and immunohistochemistry. For this reason, we selected 6 patients presenting with a myelosarcoma in combination with MDS and 12 patients revealing only uncharacteristic reactive changes of the bone marrow. Of these patients 8 developed AML following an observation time of up to 2 years. Focal leukemic infiltrates were most often localized in the skin ( n=4), oral mucosa ( n=4), lymph nodes ( n=3), gastrointestinal tract ( n=3) or pleura and retroperitoneum ( n=3 each). Myelosarcomas were usually regarded by the clinicians as putative malignant lymphomas unless further evaluation, especially involving chloroacetate esterase reactions as well as immunostaining with a panel of antibodies reactive with lysozyme, myeloperoxidase, CD68, CD43, CD56, CD117 and CD34 proved their true nature. Although at that time bone marrow findings were inconclusive, a straightforward diagnosis was reached by considering the possibility of a (primary) myelosarcoma in these patients.

[Diagnostic spectrum of Philadelphia-chromosome negative leukemic disorders]

The spectrum of Philadelphia-chromosome negative leukemoid disorders displays a large heterogeneity of clinical and morphological findings at presentation. According to the FAB guidelines as well as the WHO classification, independent subtypes with different morphological features can be distinguished. In particular, based on the degree of dysgranulopoiesis, the extent of monocytosis, basophilia and the amount of immature and mature granulocytes in the peripheral blood and the percentage of erythroblasts, most of these cases can be correctly classified as either atypical chronic myeloid leukemia (aCML) or chronic myelomonocytic leukemia (CMML). An increase in immature and dysplastic granulocytes in the blood films at presentation accompanied by granulocytic dysplasia, is the most important diagnostic parameter of aCML. On the other hand, CMML is characterized by absolute monocytosis and, as explicitly outlined by the WHO classification, may show myelodysplastic and myeloproliferative features. However, in the absence of characteristic cytogenetic or molecular abnormalities for both diseases, a minority of patients still remain who are difficult to assign to a distinctive entity, since they either show overlapping features or do not fulfill the whole set of diagnostic criteria. Furthermore, controversy and discussion arise about aCML with monocytosis and its association to CMML. Finally, leukemoid reactions and the very rarely encountered chronic neutrophilic leukemia (CNL) should be considered in patients with chronic leukocytosis. In conclusion, careful morphological analysis of bone marrow histology as well as peripheral blood films and bone marrow smears, enables the identification of patients with different prognosis and therapeutic response.