Aggressive natural killer-cell leukemia revisited: large granular lymphocyte leukemia of cytotoxic NK cells

Phase I study of dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide (SMILE) chemotherapy for advanced-stage, relapsed or refractory extranodal natural killer (NK)/T-cell lymphoma and leukemia

Extranodal natural killer (NK)/T-cell lymphoma, nasal type, and aggressive NK-cell leukemia are rare, and their standard therapy has not been established. They are Epstein-Barr virus-associated lymphoid malignancies, and tumor cells express P-glycoprotein leading to multidrug resistance of the disease. Patients with stage IV, relapsed or refractory diseases have a dismal prognosis, with survival measured in months only. To develop an efficacious chemotherapeutic regimen, we conducted a dose-escalation feasibility study of a new chemotherapeutic regimen, SMILE, comprising the steroid dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide. The components of SMILE are multidrug resistance-unrelated agents and etoposide. Etoposide shows both in vitro and in vivo efficacy for Epstein-Barr virus-associated lymphoproliferative disorders. Eligible patients had newly diagnosed stage IV, relapsed or refractory diseases after first-line chemotherapy, were 15-69 years of age, and had satisfactory performance scores (0-2). Four dose levels of methotrexate and etoposide were originally planned to be evaluated. At level 1, six patients with extranodal NK/T-cell lymphoma, nasal type, were enrolled. Their disease status was newly diagnosed stage IV (n = 3), first relapse (n = 2), and primary refractory (n = 1). All of the first three patients developed dose-limiting toxicities, and one of them died of sepsis with grade 4 neutropenia. A protocol revision stipulating early granulocyte colony-stimulating factor administration was made. Two out of three additional patients developed dose-limiting toxicities that were all manageable and transient. For the six enrolled patients, the overall response rate was 67% and the complete response rate was 50%. Although its safety and efficacy require further evaluation, we recommend a SMILE chemotherapy dose level of 1 for further clinical studies.

Progress in understanding and managing natural killer-cell malignancies

The World Health Organization classification of haematolymphoid tumours recognizes three categories of natural killer (NK)-cell neoplasms: blastic NK-cell lymphoma, aggressive NK-cell leukaemia, and extranodal NK/T-cell lymphoma, nasal-type. Recent studies indicate that CD4+CD56+ blastic NK-cell lymphoma is of plasmacytoid dendritic cell origin, and true tumours of precursor NK-cell origin may be present mainly in the CD4-CD56+ subset. Myeloid/NK-cell precursor acute leukaemia may also develop from precursor NK cells. However, because the developmental pathway of normal NK cells is not well understood, tumours of precursor NK-cell origin are not clearly identified. Among mature NK-cell tumours, extranodal NK/T-cell lymphoma is relatively common in Asia and Latin America. In localized disease, chemoradiotherapy seems to be promising, and in advanced disease, new combination chemotherapies are under active investigation. Aggressive NK-cell leukaemia is rare and has a poor prognosis. Because NK-cell neoplasms are rare and difficult to manage, rigorous studies are required for their understanding and management.

The human androgen receptor X-chromosome inactivation assay for clonality diagnostics of natural killer cell proliferations

Clonality is a frequently exploited characteristic of lymphoid malignancies. However, in the natural killer (NK) cell subset of large granular lymphocyte proliferations, clonality is difficult to prove because of the lack of specific genetic markers, such as immunoglobulin or T-cell receptor gene rearrangements. The human androgen receptor (HUMARA) assay, a polymerase chain reaction-based X-chromosome inactivation assay, is a potential diagnostic tool in these disorders. Although there is much experience with X-chromosome inactivation assays in myeloid proliferations, these assays have found only very limited application in clonality assessment of NK cell proliferations. We applied the HUMARA assay in laboratory diagnostics for detection of clonality in NK cell proliferations. We describe its test performance and report three cases in which clonality of NK cell populations was investigated by use of this assay. Our results demonstrate the usefulness of the HUMARA assay in the diagnostic workup of NK cell proliferations.

Chemokine system and tissue infiltration in aggressive NK-cell leukemia

NK cell-type lymphoproliferative disease of granular lymphocytes can be subdivided into aggressive NK-cell leukemia (ANKL) and chronic NK-cell lymphocytosis (CNKL). Hepatosplenomegaly is observed in ANKL patients, and hepatic failure is a common cause of death. Significant numbers of ANKL cells were pathologically observed in sinusoidal and interlobular regions of the liver, and in the splenic red pulp. In our previous study, ANKL cells were simultaneously positive for CXCR1 and CCR5. So, in order to elucidate the mechanism in the systemic migration of ANKL cells, we investigated the expression of the corresponding chemokines in ANKL compared with CNKL. The serum level of IL-8, MIP-1alpha and MIP-1beta was significantly elevated in ANKL patients, and ANKL cells were highly positive for IL-8, RANTES, MIP-1alpha and MIP-1beta according to intracellular staining and RT-PCR. These chemokines were also positively stained in hepatocytes. The interaction between Fas and Fas ligand (FasL) is supposed to be one of the mechanisms for liver dysfunction in ANKL. The serum concentration of soluble FasL was significantly high in ANKL patients, and ANKL cells expressed FasL protein in the cytoplasm. These results suggest that the chemokine system plays an important role in the transmigration of FasL-expressing ANKL cells.

T-cell/NK-cell lymphomas: A review

T-cell neoplasms are a group of heterogeneous neoplasms that present a challenge in management. Accurate diagnosis and classification are necessary for proper treatment. This dilemma is exemplified by continuous upgrading of classification systems in an effort to better understand these diseases. The spectrum of management varies from observation and monitoring to prompt aggressive multimodality treatment to achieve optimal outcomes. Allogeneic transplant has been successful in a minority of cases with the possibility of cure; however this approach is still largely experimental. Molecular studies such as gene expression profiling are expected to offer exciting insight into the biology of these diseases. Novel therapeutic approaches continue to be explored, however will probably require larger clinical trials to establish their utility over the current standard.

Chronic lymphocytosis of functionally immature natural killer cells

BACKGROUND

The development of natural killer (NK) cells in the bone marrow is not well characterized. We recently described a mouse (referred to as an NK cell-deficient [NKD] mouse) with a selective deficiency in NK cells caused by the insertion of a transgene construct into the genetic locus for the basic leucine zipper transcription factor ATF-2. NK cells in this mouse were both phenotypically and functionally immature and accumulated in the bone marrow at a stage at which constitutive NK cell proliferation occurs in wild-type mice.

OBJECTIVE

We hypothesized that excess IL-15 could potentially overcome this developmental block, allowing normal emigration of mature NK cells from the bone marrow to the periphery.

METHODS

Double-transgenic mice were generated by crossing the NKD mice with transgenic mice overexpressing IL-15.

RESULTS

The double-transgenic mice had a dramatic accumulation of phenotypically immature NK cells in the bone marrow and subsequently in the blood, liver, and spleen. NK cells from these double-transgenic mice manifested functional deficits similar to those observed in NK cells from NKD mice, as assessed by decreased cytokine production and cytotoxicity.

CONCLUSION

Rather than bypass the observed developmental defect in NKD mice, excess IL-15 drove a massive accumulation of phenotypically and functionally immature NK cells in the bone marrow and periphery.

CLINICAL IMPLICATIONS

We propose that these double-transgenic mice will serve as a murine model of chronic NK cell lymphocytosis in human patients.

[Primary nasal natural killer/T-cell lymphomas: classification and clinicopathological features]

BACKGROUND

Nasal NK/T-cell lymphomas are rare malignancies in Europe or North America. Histological diagnosis is difficult, because tumors imbedded in large necrotic areas and neoplastic infiltrates may be admixed with small lymphocytes, plasma cells, eosinophils, and histiocytes, and thus the process could be misdiagnosed as chronic inflammation. Progression of the disease leads to septal perforation and may also result in destruction of the hard palate, and if left untreated it ends fatally. This introduced the term "lethal midline granuloma", a term which should not be used any more.

MATERIAL AND METHODS

Clinical features, pathohistology, and current classification of primary nasal NK/T-cell lymphomas are described against the background of the recent literature and a case report.

RESULTS

Immunophenotyping is essential for the diagnosis. Tumor cells are uniformly infected by Epstein-Barr virus, which could be verified by EBER in situ hybridization. Immunohistochemically, tumor cells are positive for CD56, cytoplasmic CD3epsilon, and CD2 and they express cytotoxic molecules like granzyme B, TIA-1, GMP17, and perforin. Therapeutic options are radio- or radiochemotherapy. On average, 2- and 5-year survival rates of 50% are obtained in stages I and II. The prognosis of advanced tumor stages is very poor.

CONCLUSIONS

Immunohistochemical and molecular genetic early diagnosis is of crucial prognostic relevance.

Predicting the outcome in non-Hodgkin lymphoma with molecular markers

The World Health Organization classification divides non-Hodgkin lymphomas into B-cell, T-cell and natural killer-cell lymphomas. They are heterogeneous in epidemiology, histopathology and outcome. Clinical prognostic indices rely only on patient factors and staging. Molecular prognostic markers reflect the intrinsic lymphoma biology, measure tumour load and may provide novel therapeutic targets. Lymphomagenesis involves mutations, deletions or dysregulations of genes critical in the control of cell cycle and apoptosis, which are in turn prognostically important. Genome-wide gene expression profiling, either by allowing lymphomas to be classified according to different stages of lymphoid maturation, or by defining specific gene expression signatures, is also of prognostic significance. In lymphomas where viral infections of the neoplastic cells occur, quantification of viral copies is a surrogate marker for tumour load and hence prognosis. Molecular markers together with patient and clinicopathological features will provide more accurate prognostic models for risk stratification, in order to improve treatment outcome.

Skewed expression of natural-killer (NK)-associated antigens on lymphoproliferations of large granular lymphocytes (LGL)

Killer-immunoglobulin-like receptors (KIR) or C-type lectin-like receptors are heterogeneously expressed on NK cells and small subsets of T cells and might provide a new diagnostic tool for LGL lymphoproliferations (LGLL). We investigated the diagnostic impact of these cell surface molecules in T- and NK-type LGLL. Using three-color flow cytometry we examined the expression patterns of KIR (CD158a/b/e/i), CD85j, lectin-like receptors (CD94, CD161, NKG2A/D) and natural cytotoxicity receptors (NKp30/44/46) in 13 patients with LGLL (10 T-, 3 NK-LGLL) and compared them to those of the corresponding lymphocyte subsets in 20 control subjects. The presence of clonal TCR-gamma rearrangements and of Epstein Barr virus- (EBV) DNA were evaluated by PCR. All patients exhibited an altered expression of NK-associated markers. KIR were either lacking (6/13) or overexpressed (7/13). CD94 expression was significantly higher in all LGLL. NKG2A expression was significantly higher in NK-LGLL. Absence or overexpression was observed for NKG2A in T-LGLL and CD161 in most T/NK-LGLL. In NK-LGLL expression of NKp30 and NKp46 was significantly decreased, whereas CD85j was overexpressed. We consistently found a skewed expression pattern of novel NK markers as a pathological feature of LGLL. These antigens should be included in the diagnostic workup of this rare disease.

Primary extranodal nasal-type natural killer/T-cell lymphoma of the brain: a case report

Natural killer (NK)/T-cell lymphomas represent a rare type of lymphoma derived from either activated NK cells or, rarely, cytotoxic T cells. These lesions are most commonly extranodal and tend to present as destructive lesions within the midline facial structures. Other than the nasal cavity and paranasal sinuses, several other extranodal sites of involvement have been reported, including the pharynx, gastrointestinal tract, and testis. Although secondary involvement of the central nervous system has been reported, a convincing case of primary brain NK/T-cell lymphoma has not been previously reported. Here, we report a case of primary brain lymphoma of NK/T-cell type with a characteristic phenotype expressing CD3epsilon, CD56, granzyme B, Epstein-Barr virus-encoded small nuclear RNAs, with germline T-cell receptor gene configuration, and showing an unusual intravascular component. The patient underwent extensive imaging studies, revealing only the brain lesion. The lymphoma failed to respond to therapy and the patient eventually died after transfer to a hospice facility. This unusual case highlights an unusual presentation of a rare disease entity and highlights the need for a better understanding of the biology and treatment of T-cell lymphomas.

Aggressive NK-cell leukaemia associated with reactive haemophagocytic syndrome

We report a case of aggressive NK-cell leukaemia associated with reactive haemophagocytic syndrome in a 29-year-old Korean woman who had several small purpuric patches on both thighs. She also had high fever. Laboratory tests revealed pancytopenia and deranged liver function, and atypical lymphocytes containing toxic granules were detected from peripheral blood and bone marrow. The bone marrow examination showed diffuse histiocytic proliferation with several haemophagocytic macrophages, suggesting an associated reactive haemophagocytic syndrome. Skin biopsy from her thigh lesion demonstrated atypical CD56+ lymphoid cellular infiltrates with angiocentric pattern, and in situ hybridization test for Epstein-Barr virus was positive. Although we treated her with chemotherapy, she died 1 month later.

Large Granular Lymphocyte Leukemia

Clonal disorders of large granular lymphocytes (LGLs) represent a spectrum of biologically distinct lymphoproliferative diseases originating either from mature T cells (CD3+) or natural killer (NK) cells (CD3-). Both subtypes, T-cell and NK-cell LGL leukemia, can manifest as indolent or aggressive disorders. The majority of patients with T-cell LGL leukemia have a clinically indolent course with a median survival time >10 years. Immunosuppressive therapy with low-dose methotrexate, cyclophosphamide, or cyclosporine A can control symptoms and cytopenias in more than 50% of patients, but this approach is not curative. Several cases of an aggressive variant (CD3+ CD56+) of T-cell LGL leukemia with a poor prognosis have also been reported. Aggressive NK-cell LGL leukemia is usually a rapidly progressive disorder associated with Epstein-Barr virus (EBV), with a higher prevalence in Asia and South America. This disease is usually refractory to conventional chemotherapy, with a median survival time of 2 months. Chronic NK-cell leukemia/lymphocytosis is a rare EBV-negative disorder with an indolent clinical course. The malignant origin of this subtype is uncertain because clonality is difficult to determine in LGLs of NK-cell origin.

Cytogenetics of lymphomas

Cytogenetic analysis is now a routine part of the diagnosis and management of a significant number of lymphoid malignancies. Whilst conventional cytogenetics remains the most comprehensive method for assessing chromosome abnormalities, the technical difficulties associated with conventional cytogenetics in most lymphomas has resulted in increased use of fluorescence in situ hybridisation (FISH) to identify specific abnormalities that are useful in either the diagnosis or management of these disorders. The finding of one of the Burkitt's translocations is of major importance in the diagnosis of Burkitt's and Burkitt's-like lymphomas, whereas the t(14;18), although seen in most follicular lymphomas (FL), is not usually required to make a diagnosis. Thus, whilst cytogenetics may be of interest in FL, it is not an essential part of the diagnostic work-up. Conventional cytogenetics may be useful for identifying markers of resistance to Helicobacter pylori therapy in MALT lymphomas. In disorders such as Hodgkin lymphoma, hairy cell leukaemia and lymphoplasmacytoid lymphoma, although many cytogenetic abnormalities have been observed, no consistent or specific abnormalities have been identified and so, at this point in our knowledge of the genetics of these disorders, cytogenetics cannot be considered a useful test for either diagnosis or prognosis. In contrast, the diagnosis of mantle cell lymphoma is now dependent upon the identification of the 11;14 translocation that results in cyclin D1 up-regulation. It is widely acknowledged that FISH is the most consistently useful test to identify the juxtaposition of the CCND1 and IGH genes in mantle cell lymphoma and is regarded as the 'gold standard'. FISH also has a role in identifying genetic abnormalities of prognostic significance in chronic lymphocytic leukaemia. Given the wealth of genetic and cytogenetic abnormalities that are continuing to be found in chronic lymphoid malignancies, it will be some time before the optimal use of both conventional cytogenetics and FISH is established in the diagnosis and management of lymphomas.

An aggressive extranodal NK-cell lymphoma arising from indolent NK-cell lymphoproliferative disorder

Indolent NK-cell lymphoproliferative disorder, also known as chronic natural killer (NK) cell large granular lymphocytosis (leukemia), is a very rare entity in the World Health Organization (WHO) Classification of Tumors of Hematopoietic & Lymphoid Tissues. Unlike aggressive NK-cell leukemia, which is malignant, the WHO does not specify whether indolent NK-cell lymphoproliferative disorder is reactive or neoplastic. Patients with indolent NK-cell lymphoproliferative disorder are usually asymptomatic older adults who have a nonprogressive, very stable clinical course. We report an unusual case of an aggressive extranodal NK-cell lymphoma, non-nasal type, which presented as a subcutaneous tissue mass, which apparently transformed from a preexisting, untreated indolent NK-cell lymphoproliferative disorder in an 65-year-old otherwise healthy white man. The extranodal NK-cell lymphoma and the NK-cell lymphoproliferative disorder in the blood and bone marrow share a distinctive and identical NK-cell immunophenotype and genotype: CD56/CD8/TIA-1-positive and surface CD3-negative, negative for Epstein-Barr virus infection, and no evidence of T-cell and B-cell receptor gene rearrangements. To the best of our knowledge, such aggressive lymphomatous transformation in an indolent NK-cell lymphoproliferative disorder has not been previously reported.

Hematopoietic stem cell transplantation for natural killer-cell lineage neoplasms

Neoplasms of natural killer (NK)-lineage are rare. Their prognosis is generally poor except for cases of solitary nasal NK-cell lymphoma. The NK-cell Tumor Study Group performed a survey in Japan on patients diagnosed between 1994 and 1998. Of 228 patients selected for analysis, 40 underwent HSCT (15 allografts and 25 autografts). The underlying diseases were myeloid/NK cell precursor acute leukemia (n = 4), blastic NK-cell lymphoma (n = 11), aggressive NK-cell leukemia (n = 3), and nasal-type extranodal NK-cell lymphoma (n = 22). At the time of HSCT, 22 patients were in complete remission (CR), 11 were in relapse, and seven were primary refractory. All patients received myeloablative conditioning regimens including total-body irradiation. Sixteen died of disease progression, and six of treatment-related causes. Overall, 4-year survival was 39% with a median follow-up of 50 months; this was significantly better than that of patients who did not undergo HSCT (21%, P = 0.0003). For patients transplanted in CR, the 4-year overall survival was 68%, which was significantly better than that of patients who went into CR but did not undergo HSCT (P = 0.03). These findings suggest that the HSCT is a promising treatment strategy for NK-cell lineage.

Immunophenotyping of lymphoproliferative disorders: state of the art

Immunophenotyping was introduced into diagnostic pathology over 30 years ago to assist in the diagnosis and classification of lymphoproliferative disorders. Today the role of immunophenotyping has been expanded beyond this to include the detection of markers of prognosis, determination of disease phenotypes associated with specific chromosomal abnormalities, detection of targets for immunotherapy and to monitor residual disease. Immunoperoxidase detection methods remain the most popular in histopathology, whilst flow cytometry is most commonly applied for haematological samples. The range of monoclonal antibodies available, including those which work in routinely performed tissue specimens, continues to increase. This is in part a result of gene expression studies identifying precise genetic signatures for certain lymphoproliferative disorders and the generation of new protein markers to gene products of upregulated genes. This review summarises the current status and applications of immunophenotyping in the assessment of many of the lymphoid malignancies.

Natural killer-cell malignancies: diagnosis and treatment

Natural killer (NK)-cell malignancies are uncommon diseases. Previously known as polymorphic reticulosis or angiocentric T-cell lymphomas, they are classified by the World Health Organization as NK/T-cell lymphoma, nasal type and aggressive NK-cell leukemia. They are prevalent in Asia and South America, but exceptionally rare in western countries. Pathologically, NK-cell lymphomas show a polymorphic neoplastic infiltrate with an angioinvasive and angiodestructive pattern. Lymphoma cells are characteristically CD2+, CD56+ and cytoplasmic CD3epsilon+. T-cell receptor gene is germline, and clonal Epstein-Barr virus (EBV) infection is almost invariably. Clinically, they can be divided into nasal, non-nasal, and aggressive lymphoma/leukemia subtypes. Most nasal NK-cell lymphomas present with stage I/II disease, and frontline radiotherapy is the most important key to successful treatment. Many stage I/II patients treated with radiotherapy fail systemically, implying that concomitant chemotherapy may be needed. Chemotherapy is indicated for advanced nasal NK-cell lymphoma, and the non-nasal and aggressive subtypes. However, treatment results are unsatisfactory. High-dose chemotherapy with hematopoietic stem cell transplantation may be beneficial to selected patients. The International Prognostic Index and presentation EBV DNA load is of prognostic significance and may be useful in the stratification of patients for various treatment modalities.

Prolonged treatment response in aggressive natural killer cell leukemia

We describe a case of natural killer (NK) cell leukemia with acute presentation, systemic symptoms and hepatosplenomegaly. The uniform and aberrant phenotype of NK cells with infiltration of bone marrow and spleen was in keeping with a malignant diagnosis. Aggressive presentation was demonstrated by marked constitutional symptoms and significant tumor burden (liver, spleen, blood, bone marrow). The subsequent clinical course has been indolent, but this may have been influenced by treatment. Treatment consisted sequentially of splenectomy, intravenous pentostatin and the combination of cyclosporine A and recombinant human erythropoietin and has resulted in survival of over 48 months. We discuss the difficulties in the diagnosis of this condition, explore possible causes of cytopenia(s), and highlight the role of immunosuppression in controlling disease manifestations in large granular lymphocyte proliferative disorders.

Allogeneic haematopoietic stem cell transplantation as a promising treatment for natural killer-cell neoplasms

The efficacy of allogeneic haematopoietic stem-cell transplantation (allo-HSCT) for natural killer (NK)-cell neoplasms is unknown. We investigated the results of allo-HSCT for NK-cell neoplasms between 1990 and 2003 through questionnaires. After reclassification by a haematopathologist, of 345 patients who underwent allo-HSCT for malignant lymphoma, 28 had NK-cell neoplasms (World Health Organization classification): extranodal NK/T-cell lymphoma (n=22), blastic NK-cell lymphoma (n=3), and aggressive NK-cell leukaemia (n=3). Twelve were chemosensitive and 16 chemorefractory. Twenty-two had matched-related donors. Stem-cell source was bone marrow in eight and mobilised peripheral blood in 20. Conditioning regimens were myeloablative (n=23) and non-myeloablative (n=5). Grade 2-4 acute graft-versus-host disease (GVHD) and chronic GVHD developed in 12 and 8 respectively. Eight died of disease progression, three of infection, two of acute GVHD, one of veno-occlusive disease, one of interstitial pneumonitis, and one of thrombotic microangiopathy. Two-year progression-free and overall survivals were 34% and 40% respectively (median follow-up, 34 months). All patients who did not relapse/progress within 10 months achieved progression-free survival (PFS) during the follow-up. In multivariate analysis, stem cell source (BM versus peripheral blood; relative risk 3.03), age (>or=40 years vs. <40 years; relative risk 2.85), and diagnoses (extranodal NK/T-cell lymphoma versus others; relative risk 3.94) significantly affected PFS. Allo-HSCT is a promising treatment for NK-cell neoplasms.

Significance of chemokine receptor expression in aggressive NK cell leukemia

Natural killer (NK) cell-type lymphoproliferative diseases of granular lymphocytes can be subdivided into aggressive NK cell leukemia (ANKL) and chronic NK cell lymphocytosis (CNKL). One reason for the poor outcome in ANKL is leukemic infiltration into multiple organs. The mechanisms of cell trafficking associated with the chemokine system have been investigated in NK cells. To clarify the mechanism of systemic migration of leukemic NK cells, we enrolled nine ANKL and six CNKL cases, and analyzed the expression profiles and functions of chemokine receptors by flowcytometry and chemotaxis assay. CXCR1 was detected on NK cells in all groups, and CCR5 was positive in all ANKL cells. Proliferating NK cells were simultaneously positive for CXCR1 and CCR5 in all ANKL patients examined, and NK cells with this phenotype did not expand in CNKL patients or healthy donors. ANKL cells showed enhanced chemotaxis toward the ligands of these receptors. These results indicated that the chemokine system might play an important role in the pathophysiology of ANKL and that chemokine receptor profiling might be a novel tool for discriminating ANKL cells from benign NK cells.

Myelodysplastic syndrome of donor origin subsequent to successful treatment of myeloid/NK-cell precursor leukaemia with allogeneic PBSCT: two very rare conditions in one patient

We report a 36-year-old male with myeloid/natural killer (NK)-cell precursor acute leukaemia with a complex aberrant karyotype, who was treated according to an acute-myeloid-leukaemia (AML) treatment protocol (idarubicine, cytarabine, and etoposide) followed by high-dose cytarabine consolidation and achieved complete remission. He underwent allogeneic matched unrelated donor (MUD) peripheral blood stem-cell transplantation (PBSCT) and remained in remission throughout his remaining life. Seven months posttransplantation, a myelodysplastic syndrome (MDS) with (20q-) of donor origin was diagnosed causing severe thrombocytopenia and finally leading to infection and death. This patient represents one of the few cases published achieving remission for a significant period of time after being diagnosed with myeloid/NK-cell precursor acute leukaemia, a very rare malignant disease. We conclude, despite the fatal outcome due to infection, that allogeneic PBSCT is a therapeutic option for patients with this entity. In addition, the development of a myelodysplastic syndrome of donor origin is extremely rare and only very few cases are published worldwide.

Blastic natural killer cell lymphoma/leukemia (CD56-positive blastic tumor)

BACKGROUND

Blastic natural killer (NK) cell lymphoma/leukemia (BNKL) is an immature CD56-positive neoplasm, which was recognized recently and characterized by systemic proliferation of tumor cells including skin, lymph node, and bone marrow.

METHODS

The current study analyzed 47 patients with BNKL (27 had leukemias and 20 had lymphomas). Patient data were collected for the survey of the NK-Cell Tumor Study Group.

RESULTS

There were 33 males and 14 females, with a median age of 53 years (range, 3 months to 89 years). There were few clinicopathologic differences between the leukemia and lymphoma types. Cutaneous involvement was noted at diagnosis in 28 patients, who presented a tendency for older age of onset (median: 56 vs. 46 years, P = 0.11) than patients with noncutaneous BNKL. Cutaneous BNKL showed less frequent mediastinal involvement (4% vs. 53%, P = 0.0002) and less severe thrombocytopenia (P =0 .03). Phenotypic characteristics were also different, with cutaneous BNKL favoring CD4 and HLA-DR expression, and noncutaneous BNKL favoring CD16 and CD34 expression. Both groups responded well to chemotherapy for lymphoid malignancies, but disease recurrence was frequent. The prognosis of patients with noncutaneous BNKL was significantly poorer than that of patients with cutaneous BNKL (median survival: 15 vs. 25 months, P = 0.02). Multivariate analysis confirmed that cutaneous involvement was a significant and independent prognostic factor for BNKL, as were age of onset and leukocyte count.

CONCLUSIONS

These findings suggested that BNKL is a heterogeneous disease and contains at least two subtypes. Although further investigations are needed to settle a marker for distinction, the presence of cutaneous involvement is a useful prognostic factor.

The pathology of NK-cell lymphomas and leukemias

Natural killer (NK) cell lymphomas and leukemias are a rare but clinically important group of neoplasms. Most of these tumors are aggressive, with a high rate of mortality. They include extranodal NK/T-cell lymphomas of nasal type and aggressive NK-cell leukemias. Both are Epstein-Barr virus (EBV) associated and show similar epidemiologic features. A closely related entity seen mainly in children is hydroa vacciniforme-like lymphoma, which also is EBV positive. EBV influences the pathophysiology of these tumors, through the induction of cytokines and chemokines. The differential diagnosis of NK-cell malignancies includes fulminant EBV-associated T-cell lymphoproliferative disorder, a condition referred to in the past as fatal infectious mononucleosis. Benign proliferations of NK cells can be seen in association with viral infection. The disease formerly referred to as blastic NK-cell lymphoma is now considered to be a malignancy derived from a dendritic cell precursor.