Anti-CD34 immunoperoxidase staining in paraffin sections of acute leukemia: Comparison with flow cytometric immunophenotyping

Enumeration of CD34+ blasts by immunohistochemistry in bone marrow biopsies from MDS patients may have significant impact on final WHO classification

The percentage of blasts cells in the bone marrow (BM) of MDS patients is one of the key parameters for MDS classification and for the differential diagnosis with acute myeloid leukemia (AML). Currently, the gold standard to determine the blast percentage is conventional cytomorphology. To assess the possible impact of blast cell enumeration in BM biopsies from MDS patients on the final WHO classification using CD34 immunohistochemistry (IHC) a total of 156 BM samples from MDS and MDS-AML patients were studied and compared to blast counts by cytomorphology (CM). Eighty-nine BM aspirates were also studied by flow cytometry (FCM). Percentages of CD34+ blasts by IHC were determined blindly by two hematopathologists. Automated CD34-cell count was performed in 25 cases. Good overall agreement was found for CM and FCM with respect to critical blast thresholds (5%, 10%, 20%) (p < 0.05). However, in 17% of patients, CD34+ blast counts by IHC were higher as compared to CM with possible impact on MDS subclassification. In 7 of 21 AML patients, diagnosis was established on BM histology, while the blast percentage by CM was below the AML threshold. The assessment of CD34+ cells by IHC showed high interobserver agreement (Spearman R 0.95, p < 0.01), while automated CD34 counts were not optimal due to interference with other cellular and stromal elements. BM histology including CD34 IHC improves the diagnostic accuracy in MDS and AML. The quantification of blast cells should be based on the integration of all three methods for reliable disease classification and risk assessment.

An updated approach to the diagnosis of myeloid leukemia cutis

The diagnosis of myeloid leukemia cutis can be difficult, particularly in the context of an initial skin biopsy with a malignant hematopoietic neoplasm. We studied the immunohistochemical characteristics of 33 cases of myeloid leukemia cutis diagnosed at Stanford University Medical Center, Stanford, CA, 1996-2007, and compared them with the corresponding bone marrow blast immunophenotype and World Health Organization classification (2008). In the skin, CD43 marked 97% of cases (32/33), myeloperoxidase marked 42% (14/33), CD68 marked 94% (31/33), CD163 marked 25% (7/28), and CD56 marked 47% (14/30). CD34 and CD117 were predominantly negative. In 19 cases in which myeloperoxidase was negative, all marked with CD68 and CD43. The flow cytometric immunophenotype of the leukemic blasts in the bone marrow was discordant with the immunohistochemical profile in the skin in all cases, showing loss or gain of at least 1 antigen. Given the immunophenotypic differences between skin and bone marrow blasts, we provide an updated immunohistochemical approach to the diagnosis of myeloid leukemia cutis.

Therapy-related changes of CD34+ progenitor cells in chronic myeloid leukemia: a morphometric study on sequential trephine biopsies

In chronic myeloid leukemia (CML), it has been assumed that the number of CD34(+) progenitor cells (PGCs) provides useful diagnostic and prognostic information regarding the evolution of accelerated phase and blastic crisis. However, until now no information is available about changes of this peculiar precursor cell population during therapy or possible associations with the other bone marrow constituents. For this reason, a retrospective clinicopathological study was performed on 83 patients with CML including 209 sequential bone marrow biopsies (intervals ranging between 6 and 143 months) and immunohistological staining of CD34(+) cells (QBEND10), megakaryocyte precursors (CD61), and erythropoiesis (Ret 40f). According to treatment modalities, three different groups of patients could be distinguished that received either monotherapy by interferon-alpha2b (IFN-alpha2b) or hydroxyurea (HU) and a combination of both. In comparison with a control group, morphometry revealed a significant increase in the quantity of CD34(+) PGCs per hematopoiesis (cellularity) in the CML bone marrow before treatment. Independently of treatment modalities and presentation of clinical findings nonresponding patients were generally characterized by a higher amount of progenitors in the initial biopsy specimens. Furthermore, calculation of the CD34(+) cell growth index showed a significant and rapid progression in nonresponding patients and in those developing an accelerated or blastic phase during therapy. This feature was prominently expressed following IFN treatment and related to a failing regeneration of nucleated erythroid precursors. In patients with a myelofibrotic bone marrow at onset no differences in the number of CD34(+) PGCs were recognizable in the pretreatment biopsies. This finding contrasted a significant and gradual change in progenitor cell frequency under treatment and evolving myelofibrosis. Opposed to HU therapy, the latter feature was explicitly detectable in the IFN group. In conclusion, the incidence of CD34(+) PGCs in the CML bone marrow reflects therapeutic efficacy. By demonstrating a significant relationship between fiber content and quantity of CD34(+) cells during treatment, experimental findings concerning the complex functional interactions between the fibrous stroma compartment and progenitor cell differentiation and proliferation are elucidated.

Evaluation of bone marrow specimens with acute myelogenous leukemia for CD34, CD15, CD117, and myeloperoxidase

CONTEXT

Immunophenotyping of bone marrow (BM) specimens with acute myelogenous leukemia (AML) may be performed by flow cytometric (FC) or immunohistochemical (IH) techniques. Some markers (CD34, CD15, and CD117) are available for both techniques. Myeloperoxidase (MPO) analysis may be performed by enzyme cytochemical (EC) or IH techniques.

OBJECTIVE

To determine the reliability of these markers and MPO by these techniques, we designed a study to compare the results of analyses of these markers and MPO by FC (CD34, CD15, and CD117), EC (MPO), and IH (CD34, CD15, CD117, and MPO) techniques.

MATERIALS AND METHODS

Twenty-nine AMLs formed the basis of the study. These AMLs all had been immunophenotyped previously by FC analysis; 27 also had had EC analysis performed. Of the AMLs, 29 had BM core biopsies and 26 had BM clots that could be evaluated. The paraffin blocks of the 29 BM core biopsies and 26 BM clots were stained for CD34, CD117, MPO, and CD15. These results were compared with results by FC analysis (CD34, CD15, and CD117) and EC analysis (MPO).

RESULTS

Immunodetection of CD34 expression in AML had a similar sensitivity by FC and IH techniques. Immunodetection of CD15 and CD117 had a higher sensitivity by FC analysis than by IH analysis. Detection of MPO by IH analysis was more sensitive than by EC analysis. There was no correlation of French-American-British (FAB) subtype of AML with CD34 or CD117 expression. Expression of CD15 was associated with AMLs with a monocytic component. Myeloperoxidase reactivity by IH analysis was observed in AMLs originally FAB subtyped as M0.

CONCLUSIONS

CD34 can be equally detected by FC and IH techniques. CD15 and CD117 are better detected by FC analysis and MPO is better detected by IH analysis.

Immunohistochemistry can be used to subtype acute myeloid leukemia in routinely processed bone marrow biopsy specimens. Comparison with flow cytometry

Flow cytometry (FC) is the preferred method of immunophenotyping acute myeloid leukemia (AML). However, there are situations in which FC is unavailable and in which immunohistologic staining of bone marrow biopsy specimens can be used to provide immunophenotypic information. To evaluate immunohistologic staining and to confirm its value, we selected 80 newly diagnosed cases of AML that were classified according to French-American-British (FAB) criteria and confirmed by flow cytometric analysis for this study. Paraffin-embedded bone marrow specimens were stained using a panel of antibodies that included CD34 (QBEND10), antimyeloperoxidase (anti-MPO), antihemoglobin, factor VIII-related antigen, and 3 epitopes of CD68 (HAM56, KP1, and PG-M1). Our findings suggest that with the use of the paraffin-reactive antibodies CD34 (QBEND10), MPO, CD68 (PG-M1), antihemoglobin, and factor VIII-related antigen, immunohistochemistry can be used to subclassify AML. Comparison of immunohistochemical results with FC immunophenotyping suggests that there is significant concordance in the results for markers that can be used with both techniques, indicating that the sensitivity and specificity of both methods is comparable (P > .53 in all cases).

Immunoblot analysis of CD34 expression in histologically diverse neoplasms

CD34 is a heavily glycosylated transmembrane protein of approximately 110 kd whose function is essentially uncharacterized. First identified in a myeloid leukemia cell line, immunohistological reactivity with anti-CD34 antibodies is also encountered in a histologically diverse subset of nonhematolymphoid neoplasms including angiosarcoma, solitary fibrous tumors, epithelioid sarcomas, spindle cell lipomas, dermatofibrosarcoma protuberans, and myofibroblastomas. Immunohistological reactivity for CD34 in hematopoietic stem cells and endothelial cells has been shown to correspond to the expression of the CD34 protein. With the exception of gastrointestinal stromal tumors, CD34 protein expression has not been investigated in other CD34 immunohistologically reactive nonhematolymphoid neoplasms. We undertook this study to examine whether the observed reactivity for anti-CD34 antibodies in apparently unrelated tumors is due to the expression of the same protein or whether shared epitopes elaborated by other proteins could account for this reactivity. Immunoblot analyses with anti-CD34 antibodies of six different CD34 immunohistologically reactive lesions show the same approximately 110-kd molecular weight protein. In addition, two cases of dermatofibrosarcoma protuberans show double bands at approximately 110 kd. Laser-capture microdissection of CD34 immunohistologically reactive epithelioid sarcoma and nonreactive epidermal cells illustrates that this reactivity is specific to tumor cells. These results show that the observed immunohistological reactivity with anti-CD34 antibodies is due to the expression of the CD34 protein and not to shared epitopes on unrelated proteins.

Practical applications of immunohistochemistry in hematolymphoid neoplasms

Immunohistochemistry plays a key role in the diagnosis and classification of hematolymphoid neoplasms. New cell and lineage markers are constantly being discovered and added to the existing long list of antibodies. In this review article we provide general information and new applications of the commonly used hematolymphoid markers. We also discuss the features and applications of some newly discovered markers, such as ALK, fascin, granzyme/perforin, and tryptase. There is no universal "panel" for the diagnosis of hematolymphoid neoplasms. However, in this review article, we provide suggested panels for a given hematolymphoid neoplasm that is based on our experience and that reported in the literature.

MIC2, TdT, bcl-2, and CD34 expression in paraffin-embedded high-grade lymphoma/acute lymphoblastic leukemia distinguishes between distinct clinicopathologic entities

We propose that 12E7 (CD99) expression, along with TdT, bcl-2, and CD34 reactivity in lymphoblastic lymphoma (LyL)/acute lymphoblastic leukemia (ALL), distinguishes this group of neoplasms from small noncleaved cell lymphomas (SNCLs) in both pediatric and adult patients, thereby narrowing the differential diagnosis of high-grade non-Hodgkin's lymphomas and acute lymphoblastic leukemias in paraffin sections. 12E7 (CD99) is one of a group of available antibodies that recognizes the product of the mic-2 gene, which was originally identified in ALL. Despite this, most clinicopathological research has focused on the reactivity of 12E7 in a subset of the small round cell tumors of childhood. Although TdT is widely used in the subtyping of blastic leukemias, its use in the distinction of high-grade lymphomas in paraffin sections has been limited. We collected 24 cases of LyL/ALL (13 B-cell and 11 T-cell) and 15 cases of SNCL from 1984 through 1993. We confirmed the diagnoses using morphology and analysis of immunologic data. We performed immunohistochemistry with the 12E7 antibody, TdT, bcl-2, and CD34 on formalin-fixed, paraffin-embedded material. The patients' ages ranged from 4 to 81 years; nine of the study patients were children. Sixteen of the 24 LyL/ALLs stained with 12E7. In contrast, none of the 15 cases of SNCL reacted with this antibody (chi-square P < .0001). A larger percentage of T-cell LyL/ALLs reacted with 12E7 than did B-cell LyL/ALLs (82% v 54%). Sixteen of 20 LyL/ALLs reacted with the anti-TdT antibody, as compared with none of 11 SNCLs (chi-square P < .0001). Six LyL/ALLs were CD34 positive (of 23), and none of the SNCLs were CD34 positive (0 of 12) (chi-square P = .0519). Bcl-2-positive cases were found among both LyL/ ALLs and SNCLs, although they were more prevalent among LyL/ ALLs (92% v 25%; chi-square P < .0001). When one considers the differential diagnosis of a high-grade lymphoma/acute lymphoblastic leukemia, positive reactions with 12E7, TdT, bcl-2, and CD34 support the diagnosis of LyL/ALL over SNCL. Moreover, we present data that suggests that evaluating for TdT in formalin-fixed paraffin-embedded tissue is a more sensitive test than using either 12E7, bcl-2 or CD34 alone.

Hepatic epithelioid hemangioendothelioma: biological questions based on pattern of recurrence in an allograft and tumor immunophenotype

Epithelioid hemangioendothelioma (EHE) is best considered a vascular neoplasm of intermediate malignancy. Although usually progressive, the clinical course is highly unpredictable. The present communication describes a case of extensive recurrent hepatic EHE, limited to the liver allograft and initially manifest as an insidious seeding of individual tumor cells in areas of perivenular inflammation associated with rejection. A detailed immunophenotypic characterization of this and a small series of EHE was carried out in an effort to highlight subtle disease recurrence and to gain possible insights into tumor biology associated with this intriguing disease. In a series of five cases of hepatic EHE, CD34 (QB-END/10) was found to be more sensitive than Factor VIII (F-VIII) for recognition of the disease, similar to previous reports. The former diffusely and distinctly stained both epithelioid and dendritic tumor cells, whereas staining for the latter was focal, indistinct, and showed a high background. Although the tumor cells were negative for some markers of dendritic or macrophage maturation, such as CD1a, S100 protein, Mac 387, CD68, and LN3, there was marked infiltration of hepatic EHE by factor XIIIa + (F-XIIIa), Mac 387+, CD68+, and LN3+ macrophages and dendrocytes, most of which were interpreted as reactive. The "reactive" macrophage and dendrocyte populations were present throughout the fibrotic stroma and intermingled with the epithelioid clusters of EHE. Interestingly, a small subset of tumor cells coexpressed CD34 or F-VIII and F-XIIIa, the last of which is normally restricted to cells of the monocyte/macrophage lineage and cytokine activated microvascular endothelium in vitro. The known association of F-XIIIa+ dendrocytes with granulation tissue, repair and fibrogenesis, and the modulation of F-XIIIa and F-VIII expression by inflammatory cytokines led us to speculate that EHE lesions may derive from primitive "reticuloenothelial" cells that can differentiate along endothelial and dendritic pathways. The EHE lesions may represent a neoplastic analogue of wound healing. Thus, the variability in F-VIII staining, the strong expression of CD34, the infiltration of EHE lesions with F-XIIIa+ dendrocytes, and the coexpression of CD34 and F-XIIIa on a subset of tumor cells may have an important biological basis.

Dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans is a tumor of intermediate malignancy characterized by its aggressive local growth and marked propensity to recur after surgical excision. This article reviews the incidence, clinical presentation, histologic features, immunocytochemical studies, histogenesis, prognosis, management, and follow-up recommendations for this unusual neoplasm.

Hodgkin's Disease and Anaplastic Large Cell Lymphoma Revisited. ii. from cytokines to cell lineage

The true identity of Hodgkin's mononuclear cells and Reed-Sternberg (H-RS) cells has been a subject of controversy for decades. Those who believe that Hodgkin's disease (HD) is a heterogeneous disease may consider it to constitute lymphomas of various origins. However, this theory seems incompatible with the finding of similar phenotypic, biologic, and immunologic properties among most HD. We believe that, in the majority of cases, HD, except for LP and some LD-type HD, is a homogeneous disease despite differences in the degree of fibrosis and/or cellular reaction. The heterogeneity in cellular reactions is a result of secretion of various cytokines by H-RS cells, which may or may not be influenced by the presence of EBV. H-RS cells, and anaplastic large cell lymphoma (ALCL) cells as well, can express a combination of cytokines and cytokine receptors that is not seen in other types of lymphomas. The unique cytokine/receptor profile (e.g. the expression of c-kit-R/CD117), along with various properties associated with H-RS/ALCL cells, leads to a hypothesis that H-RS/ALCL cells are related to similar lymphohematopoietic progenitor cells with different etiologies and somewhat limited differentiation capacity. A number of H-RS cells may differentiate with limited capacity along the B-cell pathway and may be infected by EBV, which further complicates the biologic and immunologic properties of these cells. The majority of H-RS cells may also, however, differentiate along the antigen-presenting dendritic cell pathway, as indicated by the abundant expression of restin, CD15, CD40, CD54, CD58, CD80, and CD86. The majority of ALCL cells clearly differentiate to T cells, but some may acquire B-cell or histiocyte phenotypes. The progenitor cell hypothesis may explain (1) the variable expression of CD117, CD43, and CD34 as well as the absence of CD27, CD45 and CD45RA in H-RS cells; (2) the inconsistent and irregular patterns of phenotype and genotype and the various, often very limited, degrees of differentiation among these two types of lymphoma cells; (3) the existence of secondary HD or ALCL associated with rare types of lymphomas or leukemias, or vice versa; (4) the absence of recombinase and of the B-specific transcription factors BSAP; and (5) the frequent expression of IL-7 and IL-9 in H-RS cells. Copyright 1996 S. Karger AG, Basel

Establishment and characterization of a novel CD34-positive human myeloid leukemia cell line: MHH225 growing in serum-free culture

A new human multilineage myeloid leukemia cell line, MHH225, has been established in our laboratory from the bone marrow of a 60-year-old patient suffering from acute megakaryoblastic leukemia (M7); it provides a unique model for studying the effect of biologic and chemical agents on the lineage specificity of a multipotent myeloid leukemia clone containing a mixed population of megakaryoblast, erythroblast, and myeloblast cells in a serum-free culture. Morphologically, all 225 cells are large blast cells with basophilic cytoplasm containing no granules, large round nucleus containing 2-3 prominent nucleoli, and fine chromatin structure and a large nuclear/cytoplasm ratio. The MHH225 cells are CD34+HLA-DR+CD33+CD13+ with 57.6%, 28.3%, and 7.8% of them being CD41+, glycophorin A+, and CD15+, respectively, and all lymphoid-specific antigens are negative. The karyotype analysis of MHH225 cells revealed a deletion of the short arm of chromosome 7: del(7)(p13)-, a whole-arm translocation between the long arms of chromosomes 9 and 21: t(9;21)(q10;q10), and a chromosome 11 with an elongated long arm due to duplication of chromosome 11 material as well as to translocation of part of chromosome 9 onto 11q+. Also, chromosome 21 was deleted in some metaphases or showed a ring formation in other metaphases. Utrastructurally, MHH25 cells display a strong platelet peroxidase activity in the nuclear envelope and the endoplasmic reticulum. The MHH25 cells have been grown exponentially without growth factors or conditioned media or serum only in RPMI1640 culture medium. None of the myelopoietic growth factors, i.e., interleukin-3, GM-CSF, G-CSF, erythropoietin, or interleukin-6, has any effect on the proliferation and differentiation of MHH25 cells. The two, hematopoietic inhibitory cytokines, interferon-alpha and tumor necrosis factor-alpha, have only minimal growth inhibitory effect. Stem cell factor showed only weak growth-stimulatory effect on MHH225 cells but significantly inhibited chemotherapy-induced apoptosis in these cells. The new cell line MHH225 should constitute a useful model for studying stem cell antigen (CD34)-positive human multilineage myeloid leukemia cells carrying a deletion in the short arm of chromosome 7 and an aberration in chromosome 11 and provide a unique tool for investigating human hematopoietic stem cell biology and its cytokine regulation in serum-free cultures. To our knowledge, the MHH225 cell line is the first human CD34-positive leukemia cell line growing in serum-free cultures to be established.

QBEND10 for the diagnosis of myelodysplastic syndromes in routinely processed bone marrow biopsy specimens

AIM

The assessment of the value of the antibody QBEND10, which is directed against the haemopoietic stem cell related antigen CD34, in the immunohistochemical diagnosis of myelodysplastic syndrome in routinely processed bone marrow biopsy specimens.

METHODS

581 formalin fixed, paraffin embedded trephine biopsy specimens of the iliac crest were immunostained with QBEND10 (avidin-biotin complex/ABC method). The number of CD34+ haemopoietic stem cells/blast cells (referred to hereafter as CD34+ cells) was determined in each case. The Wilcoxon test was used for statistical analysis.

RESULTS

The following diagnostic categories were defined: (1) normal or reactive bone marrow (n = 356), (2) lymphoproliferative disorders, usually non-Hodgkin's lymphoma of low grade malignancy or multiple myeloma (n = 118), (3) myelodysplastic syndrome (n = 22), (4) acute leukaemia (n = 44), and (5) myeloproliferative diseases (n = 41). The average number of CD34+ cells was very low (0.2/HPF) in normal and reactive bone marrow, in lymphoproliferative disorders and in the myelodysplastic syndrome subtypes RA and RARS. Myeloproliferative diseases showed an average of three CD34+ cells/HPF. However, the average number of CD34+ cells was significantly higher (p < 0.05) in the myelodysplastic syndrome subtypes RAEB and RAEB-T (8.7/HPF) and in acute leukaemia (including both myeloid and lymphoblastic leukaemia; 111.7/HPF).

CONCLUSIONS

QBEND10 is of value for the identification of RAEB and RAEB-T in routinely processed bone marrow biopsy specimens because it enables the detection of even small increases in the number of CD34+ cells.

Bone marrow one step fixation-decalcification in Lowy FMA solution: an immunohistological and in situ hybridization study

The immunoreactivity of paraffin embedded bone marrow biopsies (BMB) was studied following a one step 20-hour-fixation-decalcification in Lowy formalin mercuric chlorid acid solution which permits excellent histological stainings. Antibodies reactive with myeloid, megakaryocytic, erythroid cells, T and B lymphocytes, mastocytes and metastatic cells were compared. Nearly all antibodies working on paraffin sections were demonstrated on Lowy FMA fixed BMB. Special care was taken to define an optimal working dilution. Trypsinization was not necessary. A slide microwave pre-treatment appeared essential before testing CD20 L26, CD8, CD3, CD34, MB1 Kappa and Lambda antibodies. It was suitable for UCHL1, LN2, CD30 antibodies. The same fixative allowed an m RNA Kappa or Lambda in myeloma and EBER 1 EBV RNAs in HIV lymphoma visualization by in situ hybridization. The safety handling of the toxic mercuric chloride component is discussed.

Diffuse sinusoidal hemangiomatosis of the spleen. A case report with enzyme-histochemical, immunohistochemical, and electron-microscopic findings

Diffuse hemangiomatosis of the spleen is a very rare benign tumor in which the whole spleen is permeated by neoplastic blood vessels. It is occasionally accompanied by severe disturbances of blood coagulation. The histogenesis of this tumor remains obscure. No systematic investigations of the immunophenotype of the neoplastic endothelium have been published. We describe a case of isolated benign diffuse hemangiomatosis of the spleen in which the enzyme-histochemical and immunohistochemical findings suggested an origin in the splenic sinus endothelial cells. Some of the tumor endothelial cells reacted with UEA-1, BMA 120, antibodies against the von Willebrand factor, CD34, and CD8, an antigen which, in man, is expressed only by suppressor/cytotoxic T cells and the endothelial cells of the splenic sinuses. Enzyme-histochemical investigations revealed reactivity for nonspecific esterase and lack of reactivity for alkaline phosphatase--a pattern typical of the sinus endothelial cells. The tumor could be distinguished from other tumors/tumor-like lesions of the spleen that exhibit endothelium with characteristics typical of the splenic sinuses (peliosis, splenoma, littoral cell angioma) on the basis of its histological features. The lack of expression of histiocytic antigens by the tumor endothelium is also evidence against a diagnosis of littoral cell angioma, which also derives from the sinus endothelium. Thus, this tumor could not be identified as any of the recognized tumors/tumor-like lesions of the spleen and it is therefore proposed that it should be designated diffuse sinusoidal hemangiomatosis.

CD34 expression by gastrointestinal tract stromal tumors

Gastrointestinal stromal tumors (GISTs) are neoplasms arising in the wall of the gastrointestinal tract that frequently show evidence of smooth muscle differentiation, either by their appearance alone or by immunohistology. A significant number of these neoplasms fail to react with any markers of muscle differentiation, however. A subset of these neoplasms have epithelioid features, and the presence of these features can give rise to confusion with other neoplasms, such as carcinomas and melanomas. Here we show that the CD34 monoclonal antibody My10 reacts with 19 of 23 (83%) of these lesions, including both those with and without epithelioid features. Five of 10 epithelioid and one of 13 spindled neoplasms lacked detectable muscle-specific actin (MSA), smooth muscle actin (SMA), and desmin; all six were CD34 reactive. Immunoblotting experiments show that the antigen on these stromal neoplasms has a molecular weight identical to that found on hematopoietic cells. The frequency and intensity of the reactivity of GISTs with anti-CD34 antibodies are distinctly higher than those reported for smooth muscle neoplasms of soft tissue and myometrium. This reactivity can be a useful adjunct in the diagnosis of difficult cases, especially in those exhibiting epithelioid morphology.

Current topics of immunohistochemistry as applied to skin tumors

Suppressor oncogene p53 is expressed more frequently in the nodular portion than the superficial spreading portion of the same melanoma. PCNA expression follows the same pattern but it is strongly expressed already in the superficial spreading portion. CD34 is found to label dermatofibrosarcoma protuberans. There is the mixture of negative strands but the immunostains are predominantly positive in the three cases studied. Neurogenic tumors are reactive but the intensity of staining is only moderate. Fibrous histiocytoma, dermatofibroma and other fibrohistiocytic tumors are non-reactive. CD34 is expressed in the outer root sheath of hair follicle below the sebaceous gland level. A case of piloepidermal cyst is CD34 positive. CD34 is expressed in vascular endothelial cells; not only hemangiomas but also lymphangiosarcoma is CD34 positive. A case of indeterminate cell histiocytosis following scabies and superficial variant of clear cell sarcoma are discussed as examples of new entities.

Expression of the human progenitor cell antigen CD34 (HPCA-1) distinguishes dermatofibrosarcoma protuberans from fibrous histiocytoma in formalin-fixed, paraffin-embedded tissue

BACKGROUND

Histologic distinction of dermatofibrosarcoma protuberans (DFSP) from fibrous histiocytoma (FH) may be difficult. In addition, differential diagnosis is hampered by the lack of appropriate immunohistochemical markers that reliably distinguish between these two entities.

OBJECTIVE

This study is aimed at the introduction of a monoclonal antibody (anti-human progenitor cell antigen-1; anti-CD34) that distinguishes between DFSP and FH in formalin-fixed, paraffin-embedded tissue.

METHODS

Paraffin-embedded specimens of DFSP, FH, and other soft-tissue tumors were investigated for CD34 expression by anti-human progenitor cell antigen-1/alkaline phosphatase-antialkaline phosphatase immunostaining.

RESULTS

Strong CD34 reactivity was present in each DFSP (n = 19) but was consistently absent from FH (n = 45) and other soft-tissue tumors (n = 47).

CONCLUSION

CD34 immunostaining of paraffin-embedded specimens may be useful in differentiating between DFSP and FH.

Minimally differentiated acute leukemia

We have studied 35 adult patients with morphologically undifferentiated peroxidase-negative acute leukemia that failed to meet the criteria for acute lymphoblastic leukemia and compared them to patients with FAB M1-M7 seen by the same physicians. The diagnosis of minimally differentiated acute leukemia (MD-AL) was associated with a higher incidence of prior hematologic disease, lower WBC, fewer blood blasts, lower marrow cellularity and a tendency towards older age. Of all patients treated with AML since January 1983, those with MD-AL were less likely to get a complete remission than those with other subtypes (35 vs 64%, p = 0.03). Treatment failure was usually due to resistant disease. Analysis of outcome as a function of drugs used during induction therapy showed an advantage for regimens containing vincristine and prednisone. The leukemic blast cells of nine patients were immunophenotyped for myeloid, lymphoid and megakaryoblast/platelet antigens. Although there were too few for a full statistical analysis as was applied to the larger group of 35 patients with MD-AL, these patients had a lower bone marrow cellularity as compared to FAB M1-M7 and a low remission rate. Eight of these were found to have positive myeloid markers and met the criteria for FAB M0. We conclude that patients with MD-AL form a distinct group with characteristic presenting features and a low response rate. Outcome data suggest that vincristine and prednisone should be included in experimental induction programs.