The demonstration of B-cell, T-cell and myeloid antigens in paraffin sections

Histology and immunohistology of bone marrow biopsy in multiple myeloma

B5-fixed/paraffin-embedded Jamshidi needle biopsies from 125 multiple myeloma patients were reviewed according to both morphological and immunohistological criteria. At microscopic examination, the following parameters were evaluated: i) grade of malignancy (low = 56; intermediate = 50; high = 19); ii) growth pattern (interstitial +/- sheets/nodules = 90; nodular = 13; packed marrow = 18; sarcomatous = 4); III) histological stage (I = 64; II = 35; III = 26). Comparison of the findings in trephine biopsies and aspirates showed that in 30% of the cases the latter led to an underestimation of the tumor burden. Immunohistochemical determination of Ig easily allowed: i) differential diagnosis from exuberant reactive plasmacytosis; ii) recognition and counting of neoplastic plasma cells; iii) detection of minimal residual disease after treatment. Immunohistochemistry also confirmed phenotypic aberration of neoplastic plasma cells, showing positivity for CD45, EMA, and cytokeratins in 14%, 59%, and 25% of the cases, respectively. Furthermore, it displayed expression of the P-glycoprotein in 4/8 resistant cases. These findings underline that routinely processed Jamshidi needle biopsies can be of great value in the study of patients with multiple myeloma.

Complex pathological diagnosis of granulocytic sarcoma: apropos of a case

The diagnosis of granulocytic sarcoma can be very difficult when there is no demonstrable abnormality in the peripheral blood or bone marrow. We present the diagnostic algorithm of granulocytic sarcoma by reporting on a case mimicking large cell lymphoma without previous manifestation of acute myeloid leukemia or a myeloproliferative disorder. After standard histoprocessing, we used immunohistochemical and molecular biological methods to analyze our case. The lymph node showed diffuse infiltration of immature blast cells resembling large cell lymphoma. However, immunohistochemistry did not support this diagnosis. The tumor cells showed LCA, bcl-2, CD43, CD34 and myeloperoxidase positivity. We also detected bcl-2 gene rearrangement. In case of a lack of a specific histological picture, particularly in poorly differentiated tumors, only some minor histological signs in combination with immunohistochemistry and molecular diagnostic methods can help to render the correct diagnosis.

Practical utility of the revised European-American classification of lymphoid neoplasms for Japanese non-Hodgkin's lymphomas

A clinicopathological study of 515 non-Hodgkin's lymphoma (NHL) cases was performed using the revised European-American classification of lymphoid neoplasms (REAL classification) in an HTLV1-nonendemic area of Japan. The following characteristics were revealed: 1) frequency of extranodal lymphomas was high (59%) with 79% B-cell lymphomas in this series, while the overall ratio of B:T/NK lineage was 3.7:1; 2) the most common type was the diffuse large B-cell lymphoma (46%), follicle center lymphomas occurred at an incidence lower (15%) than that in European and American populations, and marginal zone B-cell lymphomas accounted for as much as 12%; 3) peripheral T-cell lymphomas were common (19%), with the unspecified type predominant (11%), while adult T-cell lymphomas were present at a level equivalent to that among European and American patients (1%). Clear segregation of survival curves was rated according to cell lineage and B-cell lymphomas had a better prognosis than T / NK-cell lymphomas. Furthermore, new subtypes in the REAL classification, such as marginal zone B-cell and mantle cell lymphomas, exhibited distinct curves. Taken altogether, the REAL classification demonstrated advantages for assessment of Japanese NHL cases.

Differences in clinicopathological characteristics and major prognostic factors between B-lymphoma and peripheral T-lymphoma excluding adult T-cell leukemia/lymphoma

A total of 541 consecutive patients treated between 1975 and 1985, 449 with B-lymphoma and 92 with peripheral T-lymphoma, excluding adult T-cell leukemia/lymphoma (ATL), termed peripheral non-ATL T-lymphoma, were analysed. Clinicopathological features that were predominantly associated with B-lymphoma were low and intermediate grades (defined by the Working Formulation), diffuse large cell type, stage II disease, bulky disease, favourable extranodal sites that are defined as a group of primary tumors such as the eye, Waldeyer's ring, thyroid, and stomach, while other features predominantly associated with peripheral non-ATL T-lymphoma were high grade pathology, diffuse mixed-cell and immunoblastic type, systemic "B" symptoms, poor performance status (PS), generalized lymphadenopathy, involvement of organs such as liver, skin, and nose, leucocytosis, and a high levels of serum alkaline phosphatase. The survival curve for B-lymphoma was better (P < 0.01) than that for peripheral non-ATL T-lymphoma. Multivariate analysis revealed that the major prognostic factors were pathology, stage, and primary site for B-lymphoma, while stage, PS, and total protein levels were important for peripheral non-ATL T-lymphoma. These results indicate that B- and peripheral non-ATL T-lymphomas appear to have different biological characteristics.

Immunophenotypic analysis of extranodal non-Hodgkin's lymphomas in the oral cavity

Fifty cases of extranodal non-Hodgkin's lymphoma arising in the oral cavity were reclassified using the updated Kiel classification. In order to determine the antigenic phenotype of the proliferating cells in oral lymphoma, we used a panel of paraffin effective antibodies that are known to react with lymphocyte- and histiocyte-associated antigens. The median age of the patients was 53 years, with a male predominance (M:F = 1.9: 1). The great majority of oral non-Hodgkin's lymphomas were B-cell lymphomas. There were 12 low-grade B-cell lymphomas (comprising one mucosa-associated lymphoid tissue, four centrocytic and seven centroblastic-centrocytic lymphomas) and 25 high-grade tumors (comprising 17 centroblastic, two immunoblastic, two Burkitt's and four lymphoblastic lymphomas). All 37 B-cell malignancies showed reactivity for L 26 and KiB 3. A monotypic immunoglobulin staining pattern, as revealed by light chain restriction, was found in 21 cases (57%) of the non-Hodgkin's lymphomas confirming their B-cell origin. Furthermore, monotypic staining for kappa-chain predominated (16/21 kappa, 5/21 lambda). Only a small number (6 cases) was of T-cell lineage and all cases showed positive reaction for UCHL 1, MT 1 and DFT 1. In one of six T-cell lymphomas, Ber-H 2 positive anaplastic large cell lymphoma was detected. Such a case was documented for the first time in the primary extranodal non-Hodgkin's lymphoma of the oral cavity. Five cases could be assigned with certainty to the histiocytic system. These cases were positive for cathepsin D and KP 1 LN 3, which recognized Ia (HLA-DR) antigens, was demonstrated most frequently in high-grade B-cell lymphomas, T-cell lymphomas and true histiocytic lymphomas.

Roles of Langerhans' cells and T-lymphocytes infiltrating cancer tissues in patients treated by radiation therapy for cervical cancer

Correlations between infiltration of immunologic cells in tumor tissues and prognosis of radiation therapy were investigated for 275 patients with cervical cancer who were treated with radiation therapy alone, including 216 patients with Stage III squamous cell carcinomas and 59 with adenocarcinomas of all stages. Langerhans' cell (LC) and T-cell were stained immunohistochemically on the specimens excised from the cervical cancer. In squamous cell carcinoma, 5-year survival rates for patients with LC infiltration were significantly better than those without LC (78% versus 60%; P < 0.01). The 5-year survival rate of patients with T-cell infiltration also was significantly better than that of patients without such infiltration (83% versus 61%; P < 0.05). Similar trends were observed in patients with adenocarcinoma; 5-year survival rates for patients with LC infiltration and those without LC infiltration were 49% and 25%, respectively (P < 0.025). The survival rates for patients with T-cell infiltration and those without were 50% and 33%, respectively (P < 0.1). An analysis of patterns of failure of radiation therapy demonstrated that the favorable prognosis in LC infiltration was attributable mainly to improvement of local control rates, but that in T-cell infiltration was not. T-cells infiltrated into tumor specifically in the patients with LC infiltration in both cell types. The authors suggest that the host anti-cancer immune response of individual patients may be remarkably different at the first step of antigen recognition by LC. The LC may induce T-cell-mediated antitumor response and improve local response in radiation therapy.

Primary non-Hodgkin malignant lymphoma of the breast. An immunohistochemical study of seven patients and literature review of 152 patients with breast lymphoma in Japan

BACKGROUND

The breast is rarely a primary site for extranodal malignant lymphoma. Most reported primary non-Hodgkin malignant lymphomas of the breast (PBL) are of B-cell phenotype.

METHODS

Histologic and immunohistochemical analyses of seven patients with PBL and a statistical analysis of 152 patients with PBL reported in the Japanese literature were performed.

RESULTS

Malignant lymphoma could not be predicted preoperatively with clinical and radiologic findings; breast carcinoma, fibroadenoma, and phyllodes tumor were the preoperative diagnoses. All patients were women; they ranged in age from 31 to 80 years (mean, 57.6 years). The right breast was involved initially in five patients. In four, only the breast was involved (Stage I), whereas in three, the ipsilateral axillary lymph nodes (Stage II) were involved at diagnosis. According to the Working Formulation, all patients belonged to the intermediate grade and were classified as having diffuse large cell (five patients) or mixed (two patients) lymphoma. Immunophenotypic analysis revealed that all patients had B-cell lymphoma. No patients had lymphoepithelial lesions, which is the characteristic feature in categorizing a lymphoma as a mucosa-associated lymphoid tissue (MALT) lymphoma. A statistical analysis of the patient reported in the Japanese literature has divided PBL into two types: a bilateral type that affects younger women and a unilateral type that has a broad age distribution, but preponderantly occurs in older women. The age and stage at diagnosis were significant prognostic factors in predicting the survival time, but the location and size of the tumor at initial presentation, histopathologic type, terminal leukemic manifestation, and treatment modality were not.

CONCLUSIONS

This study indicates that most PBL are diffuse large cell lymphoma of B-cell phenotype and that the age and stage at diagnosis are significant prognostic factors.

CD43 expression in B cell lymphoma

AIMS

To determine the expression of CD43 in frozen sections in a range of B cell lymphomas.

METHODS

The monoclonal antibody WR14, clustered provisionally in the Fourth Leucocyte Typing Workshop as a CD43 reagent, was investigated by epitope blocking studies on formalin fixed reactive lymph node tissue, using the established CD43 antibody MT1, to validate its use as a CD43 reagent. CD43 expression was studied in 131 immunophenotypically defined B cell lymphomas, including lymphocytic lymphoma (Lc, n = 13), centrocytic lymphoma (Cc, n = 14), and a range of follicle centre cell lymphomas (FCC) including centroblastic/centrocytic follicular (CbCcF, n = 48), centroblastic diffuse (CbD, n = 39), centroblastic/centrocytic diffuse (CbCcD, n = 4), centroblastic follicular and diffuse (Cb FD, n = 3) and centroblastic/centrocytic follicular and diffuse (CbCc FD, n = 1). Nine lymphomas of mucosa associated lymphoid tissue (MALT) were also examined.

RESULTS

Epitope blocking studies showed that WR14 is a CD43 reagent that binds to an epitope identical with or close to that recognised by MT1. Eleven of 13 (84%) cases of Lc and 11 of 14 (78%) cases of Cc expressed CD43; 87 of 95 (91%) cases of FCC did not. All eight low grade lymphomas of MALT were negative. One high grade lymphoma, transformed from a low grade MALT lymphoma, was positive for CD43. The expression of CD43 by tumours of B cell lineage was associated with the expression of CD5 (p < 0.001) although either antigen could occasionally be found in the absence of the other.

CONCLUSION

CD43 reagents can be used in conjunction with CD5 antibodies for the immunophenotypic discrimination of follicle centre cell lymphomas from non-follicle centre cell lymphomas.

Monoclonal antibody OPD4 detects neoplastic T cells but does not distinguish between CD4 and CD8 neoplastic T cells in paraffin tissue sections

Monoclonal antibody (MoAb) OPD4, reported to preferentially react with benign CD4 T cells in formalin-fixed tissue sections, was examined for its reactivity with 56 T-cell neoplasms after formalin or Bouin's fixation to determine if it also preferentially detects neoplastic CD4 T cells in paraffin tissue sections. Monoclonal antibody OPD4 did not preferentially detect neoplastic CD4 T cells, since it reacted with 22 of 38 (58%) CD4-positive compared with nine of 14 (64%) CD4-negative T-cell neoplasms. However, MoAb OPD4 appears to detect neoplastic T cells in Bouin's-fixed (11 of 20 cases [55%]) about as well as in formalin-fixed (20 of 32 cases [63%]) tissues. Since MoAb OPD4 does not preferentially react with neoplastic CD4 T cells, the utility of this MoAb as a pan-T-cell marker in routinely processed tissues was also explored and compared with that of Leu-22, UCHL-1, and CD3. All four antibodies reacted with approximately the same percentage of T-cell malignancies (51% to 57%). However, examination of different clinicopathologic groups and types of fixative highlighted differences. Monoclonal antibodies OPD4 and Leu-22 reacted with 62%, while CD3 detected only 41% of formalin-fixed, postthymic T-cell neoplasms. OPD4, UCHL-1, and CD3 each reacted with 55%, but Leu-22 recognized only 45% of Bouin's-fixed, postthymic T-cell malignancies. OPD4 reacted with none, but CD3 reacted with all four T-cell lymphoblastic lymphomas. Various antibody combinations were examined to determine an optimal panel for the recognition of T-cell neoplasms in paraffin sections. The combination of MoAbs OPD4 and Leu-22 detected 86% of postthymic T-cell neoplasms in formalin-fixed tissue sections. Furthermore, MoAb OPD4 appears to be relatively specific for T-cell neoplasms, detecting 31 of 56 (55%) T-cell malignancies, while only reacting with two of 39 (5%) B-cell neoplasms. Therefore, while not preferentially reactive with neoplastic CD4 T cells, MoAb OPD4 may be useful as a pan-T-cell marker of postthymic T-cell neoplasms in routinely processed, formalin-fixed tissues, especially when used in conjunction with MoAb Leu-22.

Whipple's disease: a histological, immunocytochemical and electronmicroscopic study of the immune response in the small intestinal mucosa

Whipple's disease is a multisystem disorder with protean manifestations and with poorly understood aetiopathogenesis. It is unclear how the immune system reacts, whether it functions normally or not, whether it protects the organism or is defeated in one way or another by the 'Whipple bacillus'. The purpose of our study was to assess humoral and cellular immunity at the level of the intestinal mucosa. This histochemical, immunocytochemical and electronmicroscopic study, based on 16 cases, has shown that the changes in components of the mucosal immune system in Whipple's disease are quite different from normal. The phagocytic capacity of the macrophages, assessed microscopically, is abnormal, the number of intra-epithelial lymphocytes is increased, the CD 4/CD 8 cell ratio is decreased and the IgM positive cells in the lamina propria outnumber the IgA positive cells. These changes may be inter-dependent.

Value of immunohistochemistry in the diagnosis of leukemia cutis: study of 54 cases using paraffin-section markers

A grave prognosis is usually associated with leukemic skin infiltrates (leukemia cutis). However, some leukemic skin infiltrates are clinically similar to reactive non-leukemic infiltrates in patients with leukemia; thus it is of great importance to distinguish them. Fifty-four cases which were thought clinically to be leukemia cutis underwent immunophenotyping with a panel of nine T, B, monocytic, and macrophage markers using paraffin sections. Immunohistochemistry helped identify 44 cases with leukemia cutis and 10 with reactive infiltrates. In all cases of leukemia cutis, the staining patterns of skin infiltrates were concordant with cell type in the bone marrow. Furthermore, the panel of markers was usually helpful in distinguishing reactive from leukemia infiltrates, especially in cases with chronic lymphatic leukemia. Immunohistochemistry is a valuable adjunct in histopathologic differentiation of skin infiltrates in most cases of leukemia. With formalin-fixed, paraffin-embedded biopsies, we recommend that CD45 (LCA), CD45RO (UCHL-1), CD3, CD20 (L-26), CD43 (Leu-22), CD68 (KP-1), lysozyme, and chloroacetate esterase be considered in cases of systemic leukemia with cutaneous papules and nodules that prove difficult to interpret with routine section.

Nuclear morphometry of primary B cell thyroid lymphoma

Thyroid lymphoma is usually distinguished from anaplastic thyroid carcinoma and from Hashimoto's thyroiditis by morphological and immunohistochemical assessment of tissue sections. Our objective was to assess the value of nuclear morphometry in the differential diagnosis of these conditions. Nuclear area measurements were performed on 10 cases of thyroid lymphoma using an IBAS 2000 Image Analyser and compared with similar measurements performed on 10 cases of Hashimoto's thyroiditis and 2 of anaplastic thyroid carcinoma. It was found that karyometry demonstrated differences between all three conditions, the cases of thyroiditis being distinguishable from lymphoma on the basis of mean nuclear area alone. Mean nuclear area for lymphomas was greater than for Hashimoto's thyroiditis and lower than for anaplastic carcinomas. The mean nuclear area also reflected the grade of lymphoma, with the exception of one case which had a large reactive T cell population. It is concluded that nuclear morphometry provides valuable information in the diagnosis and assessment of thyroid lymphomas.

Plasmacytoid monocyte proliferation associated with myeloproliferative disorders

Plasmacytoid T-cell (PTC) lymphoma is a rare clinicopathologic entity characterized by generalized lymphadenopathy in association with a myeloproliferative disorder. Hepatosplenomegaly and weight loss frequently are present. Nodal T-zone expansion by mononuclear cells with ultrastructural and immunohistochemical features typical of PTC is diagnostic. All of the five previously reported cases of PTC lymphoma coincided with or heralded the onset of a clinically aggressive myeloid leukemia. This strong association and recent immunohistochemical findings in reactive or neoplastic PTC favored a monocyte/macrophage derivation of these cells, and it has been suggested that they be renamed plasmacytoid monocytes (PM). Two additional cases of PTC lymphoma were studied at the institutions of the authors, and the findings supported the concept that PTC belong to the monocytic lineage. The disease presentation was generalized lymphadenopathy with constitutional symptoms. One patient also had hepatosplenomegaly and bilateral renal enlargement concomitantly with myelofibrosis with myeloid metaplasia that progressed within months to acute myelogenous leukemia. Similar rapid evolution of acute monoblastic leukemia occurred in the other patient. Tumor cells within subtotally effaced lymph nodes had positive findings for CD45, CD4, CD7, and LN2 and negative findings for CD3, CD8, and beta F1. Occasional cells had positive findings for CD2. One case demonstrated CD5, HLA-DR, CD71, and CD43 (Leu-22)-positive cells. The myeloid/monocyte-associated antigens CD14 and CD68 were identified in both. The tumor cells lacked the B-cell markers LN1, CD20 (L26), CD19, and CD22 and did not rearrange immunoglobulin heavy chain genes and T-cell receptor beta, gamma, and delta chain genes. The term plasmacytoid T-zone lymphoma or PM proliferation is more appropriate for this rare disease. The close association of the PM proliferation with a myeloproliferative disorder indicates that the two entities are related.

Lymphocyte markers on formalin-fixed tissue in Jessner's lymphocytic infiltrate and lupus erythematosus

Clinical and histological differentiation between Jessner's lymphocytic infiltration of the skin (JLI) and lupus erythematosus (LE) may be difficult. Previous immunohistochemical studies using monoclonal antibodies on frozen sections have shown that the majority of inflammatory cells in JLI and LE are T lymphocytes, whereas B lymphocytes are few or absent. We have performed an immunohistochemical study on formalin-fixed, paraffin-embedded tissue sections from seven patients with JLI and five with LE using monoclonal antibodies MT1 (pan T-cells), OPD4 (helper/inducer T-cells CD4), MT2 (mantle zone B and some T-cells), MB2 (pan B-cells), L26 (pan B-cells), and LN1 (germinal centre B-cells). In both diseases, the-majority of the inflammatory cells were T lymphocytes (MT1 positive), confirming the results others have obtained on frozen material. OPD4 positive cells were detected in varying numbers in all cases. However, the percentage of B lymphocytes tended to be higher in JLI than LE. LN1 was the most useful B-cell marker in distinguishing JLI from LE. However, a combination of MT2 and LN1 gave the most significant difference. We conclude that immunohistochemical analysis using a panel of monoclonal antibodies to T and B lymphocytes may be useful in differentiating JLI from LE, although there is still considerable overlap.

Tissue level lymphocyte subpopulations in donovanosis

Total T-, B-, T4-, and T8-lymphocyte populations were estimated in tissue sections of ulcers from 22 donovanosis patients, comprising 17 ulcerogranulomatous, four hypertrophic, and one sclerotic variants, using monoclonal antibodies and immunohistochemical technique (PAP). T- and B-lymphocytic infiltrations in the tissues were almost identical, without any significant difference in ulcerogranulomatous and hypertrophic variants. The T4:T8 ratio in ulcerogranulomatous variants, however, was 1.41, which was significantly higher than that of hypertrophic variants (1.28), indicating a greater cell-mediated immune response in the former than in the latter. This is substantiated by the documentation of a paucity of Donovan bodies, both in the tissue smear and slow (overnight) Giemsa-stained tissue sections, in the ulcerogranulomatous variant.

The immunopathology of Schistosoma mansoni granulomas in human colonic schistosomiasis

The immunopathology of Schistosoma mansoni infection was studied in colonic biopsies obtained from 14 patients with established schistosomiasis. The characteristic lesions of this parasitic infection are mainly induced by the presence of living eggs in the tissue. Different types of lesions can be present simultaneously. The earliest lesions contain T-lymphocytes as well as accessory cells around living eggs. They transform into granulomas composed of eosinophils, T-lymphocytes, a few B-lymphocytes and large mononuclear cells expressing major histocompatibility (MHC) class II antigens. These cells are also Mac 387 positive. This means that they are monocytes/macrophages freshly recruited from the blood. In other, probably older, granulomas, MHC class II positive cells tend to disappear and the centrally located multinucleated giant cells are negative for antibodies directed against MHC class II antigens. It appears thus that the composition of the granulomas in schistosomiasis is variable. The lesions may have characteristics of cell-mediated immunity and/or of a foreign-body reaction. Contrary to what is often seen in Crohn's disease or intestinal tuberculosis no major hyperplasia of the lymphoid tissue is observed in the colon in association with S. mansoni infection.

Computer assisted selection and assessment of antibodies in the diagnosis of lymphomas

With increasing numbers of reagents the problem of selecting appropriate antibodies to solve problems in the diagnosis of lymphoma is becoming more complex. One approach is to use a computer program to optimise the selection process. Such a program was devised, incorporating data from an extensive literature search. When presented with a differential diagnosis it selects the most appropriate antibody panel and when given the results evaluates the relative likelihood of each possible diagnosis. In a retrospective study 81% of the tests used had been non-discriminatory, but using the results of the remaining 19% of the tests, the computer was able to select the "correct" diagnosis with a high degree of certainty. The development and use of this system illustrated several problems in the application of computer assisted diagnostic techniques in histopathology. These problems include incomplete data and lack of understanding of the process of histopathological diagnosis.

Non-Hodgkin's lymphoma of the major salivary gland: a morphologic and immunohistochemical study of 15 cases

A total of 15 cases of Japanese salivary gland lymphoma was analysed by conventional histology and also by immunoperoxidase staining of paraffin sections. The initial sites included: parotid gland (14 cases, 93%) and submandibular gland (1 case, 7%). The mean age was 59 yr, with a male to female ratio of 2.8:1. The only one patient (Case 9) with clinical evidence of Sjögren's syndrome showed the development of intrasalivary malignant lymphoma. Each lymphoma was classified according to the Working Formulation for Clinical Usage. The Working Formulation grades were 20% low, 67% intermediate, and 13% high. These neoplasms fell into six categories: follicular, small cleaved type (1 case); follicular, mixed small cleaved and large cell type (2 cases); follicular, large cell type (2 cases); diffuse, mixed small and large cell type (1 case); diffuse, large cell type (7 cases); and large cell, immunoblastic type (2 cases). Fifteen tumors were studied using a indirect immunoperoxidase method. A selected antibody panel was used, including B-cell markers (immunoglobulins, Ki-B3, L26), T-cell markers (UCHL-1 and MT1) and histiocytic markers (lysozyme, alpha 1-antitrypsin and cathepsin D). Eleven cases reacted with pan-B-marker (Ki-B3 and L26) and eight of them showed the presence of monoclonal cytoplasmic immunoglobulin (C-Ig). Following rigid criteria, monoclonal C-Ig of M kappa was demonstrated in one case of follicular, small cleaved cell type, one follicular, large cell type and two diffuse, large cell type; M lambda was demonstrated in one diffuse, large cell type; and G lambda was demonstrated in one follicular, mixed small cleaved and large cell type, and two diffuse, large cell type.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical differential diagnosis of granulocytic sarcomas and malignant lymphomas on formalin-fixed material

A panel of monoclonal antibodies (anti-CD45 [common leukocyte antigen], Ki-B3, L26, MT1, UCHL1, anti-CD15 [X-hapten], anti-neutrophil granule protein elastase [NP57]), anti-lysozyme, and the naphthol-ASD-chloroacetate reaction were applied to two cases of granulocytic sarcoma (GS) for evaluation of their utility in differentiating GS from malignant lymphoma. Lysozyme and naphthol-ASD-chloroacetate esterase were found to be the most reliable markers for detection of the myeloid nature of the tumour cells. GS infiltrated solely the mucosa of the nasal cavity in one case, while in the other it involved both the nasal cavity and maxillary sinus with simultaneous eruptions on the skin of the trunk. In both cases, peripheral blood and bone marrow findings were inconspicuous at the time of diagnosis of GS.

Primary lymphomas of the lung: morphological, immunohistochemical and clinical features

Sixty-two cases of primary malignant lymphoma of the lung were investigated. Fifty-eight lymphomas were of B- and two of T-cell type. Two cases of high-grade lymphoma could not be further classified. The largest group (43 cases) consisted of low-grade B-cell lymphoma of the bronchus-associated lymphoid tissue. These showed features similar to low-grade B-cell lymphomas of the mucosa-associated lymphoid tissue of the stomach. The low-grade lymphomas showed a peak occurrence in the sixth decade, the high-grade lymphomas in the seventh decade. Males predominated slightly. Three-quarters of the patients with low-grade B-cell lymphoma of the bronchus-associated lymphoid tissue showed solitary or multiple sharply defined nodules of the lung. The prognosis of the B-cell-derived lung lymphomas without constitutional symptoms was relatively favourable, regardless of whether they were of low- or high-grade malignancy, whereas patients with constitutional symptoms and the two patients with T-cell lymphomas showed a bad prognosis. However, recurrences and metastases in the lung, stomach, lymph nodes and salivary glands were seen in about 46% of the cases of low-grade B-cell lymphoma of the bronchus-associated lymphoid tissue.

Reactive proliferative lesions in lymph nodes from rheumatoid arthritis patients. A clinicopathological and immunohistological study

In 22 cases of rheumatoid arthritis (RA), including 4 cases of malignant RA (MRA), reactive proliferative lymph node lesions were studied clinicopathologically and immunohistochemically. This series included 5 males and 17 females. The period between disease onset and lymph node biopsy ranged from 3 months to 41 years. Generalized lymphadenopathy was noted in 13 cases and constitutional symptoms in 8. The histological findings characteristic of RA were 1) follicular hyperplasia with active germinal centers and 2) polyclonal plasma cell infiltration in the interfollicular area. Studies of intracytoplasmic immunoglobulin showed that gamma-heavy chain-expressing plasma cells were a major component in the interfollicular area in 17 RA cases. However, in 4 MRA cases, a prominent increase of mu chain-expressing plasma cells was recognized in the same area. In the 3 cases for which fresh tissue sections were stained with monoclonal antibodies against lymphocytes, we found that the majority of T cells in the interfollicular area had helper/inducer markers. The identical locations of the T cell population and plasma cells indicated that both played a role in the proliferation and/or differentiation of B cells in lymph nodes in RA.

Immunophenotyping of cutaneous lymphoid infiltrates in frozen and paraffin-embedded tissue sections: a comparative study

A panel of antibodies reactive in routinely fixed, paraffin-embedded tissue sections was compared with a panel of antibodies reactive in frozen sections for the immunophenotyping of cutaneous lymphoproliferative disorders. Three T cell-associated markers (UCHL1, MT-1, MT-2, six B cell-associated markers (MB-1, MB-2, LN-1, LN-2, L-26, 4KB5), immunoglobulin heavy and light chains, anti-LCA antibody, two markers for Reed-Sternberg cells (Ber-H2, Leu-M1), one marker for macrophages (Mac-387) and anti-S-100 protein antibody were tested on normal skin, inflammatory skin diseases, and cutaneous lymphomas and pseudolymphomas. On the basis of the results in frozen sections, 12 inflammatory T cell diseases, 14 T cell lymphomas and pseudolymphomas, and 10 B cell lymphomas and pseudolymphomas were identified. In addition, two cases of specific skin infiltrates of Hodgkin's disease have been examined. Among T cell markers, the greatest sensitivity was exhibited by UCHL1, which stained all but one specimen of T cell infiltrate; it was negative in one specimen of mycosis fungoides that progressed into a T-immunoblastic lymphoma. The combined use of MB-2, LN-2, and 4KB5 identified all B cell proliferations. LN-1 marked germinal centers in all cases of follicular lymphoma and pseudolymphoma. Ber-H2 stained the Reed-Sternberg cells in both cases of Hodgkin's disease and the large cells in the histiocytic type of lymphomatoid papulosis. Mac-387 and anti-S-100 protein antibody recognized macrophages and T-zone histiocytes (Langerhans cells and interdigitating cells), respectively. A panel of antibodies reactive in routinely fixed, paraffin-embedded tissue sections is proposed that facilitates the identification of most B and T cell infiltrates in the skin.

Distribution of non-lymphoid, inflammatory cells in chronic HBV infection

Non-lymphoid cells play a key role in the initiation and maintenance of cellular immune responses. Using in-situ immunohistochemical techniques and a panel of monoclonal antibodies (mcabs) reactive with B5-fixed, paraffin-embedded liver biopsies, we analysed the non-lymphoid cell component in inflammatory infiltrates in 20 cases of chronic hepatitis B virus (HBV) infection. In addition, lymphocyte subsets and HLA-DR antigens were studied. Mcab KP1 labelled scattered Kupffer cells, which variably expressed HLA-DR antigens. Their random distribution and lack of significant topographical association with lymphocytes suggest that classical Kupffer cells do not play a major role in cell-mediated immune reactions. On the other hand, mcab Mac387 was unreactive with normal liver tissue but labelled HLA-DR+ dendritic cells in areas of intralobular inflammation. On (immuno)electron microscopy, these Mac387+ dendritic cells were situated in the Disse space, where they formed close contacts with lymphocytes. Similar dendritic cells were situated at the edge of portal tracts in cases of chronic active, but not chronic persistent hepatitis. Immunostaining on serial frozen sections revealed their close topographical association with cytotoxic/suppressor T-cells, suggesting that Mac387+ HLA-DR+ dendritic cells play an immunomodulatory role in the effector arm of the cellular immune response that takes place in the periphery of portal tracts and the lobular parenchyma, and that involves activation and proliferation of cytotoxic T cells. Finally, large Mac387- HLA-DR+ dendritic cells expressing the LN2 marker were situated amidst helper/inducer T-cells in the centre of severely inflamed portal tracts.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte predominance Hodgkin's disease--an immunohistochemical study

Lymph node biopsies from 57 local and referred cases, previously diagnosed at Southampton between 1978 and 1987 as lymphocyte predominance Hodgkin's disease were examined using the monoclonal antibodies MT1, UCHL1, L26, LN-1, E29/68 (EMA), Leu-M1 (CD15) and Ber-H2 (CD30). Of the 34 cases with a nodular architecture, 21 (19 male, two female) contained polylobated Reed-Sternberg cell variants with a B-cell phenotype, which lacked expression of CD15. In all cases, the polylobated cells showed positive staining with L26 and LN-1. Six cases expressed EMA and three showed positive staining with Ber-H2. Two cases lacking polylobated cells were reclassified as reactive follicular hyperplasia with progressive transformation of germinal centres. The remaining 11 cases had an atypical immunophenotype and were reclassified, mainly as mixed cellularity Hodgkin's disease. In six cases, the lymph node architecture showed a mixture of nodular and diffuse growth patterns. Five of these cases contained polylobated cells with the typical morphology and immunophenotype of those seen in nodular lymphocyte predominance Hodgkin's disease. The sixth case contained cells expressing CD15, and was reclassified as nodular sclerosing Hodgkin's disease. Of the fifteen biopsies with a diffuse architecture, four contained polylobated B-cells lacking expression of CD15. These were considered to be diffuse lymphocyte predominance Hodgkin's disease. The remaining 11 cases were reclassified as either Hodgkin's disease, mixed cellularity or as T-cell lymphomas.

The plasmacytoid T cell or plasmacytoid monocyte--a sessile lymphoid cell with unique immunophenotype and unknown function, still awaiting lineage affiliation

Clusters of cells with a plasmacytoid appearance have been identified in T zones of human lymphoid tissue. These cells were shown to express the CD4 antigen in the absence of B-cell antigens. Thus, they were named "plasmacytoid T cells" (PTCs). Recent studies, however, have suggested a myelomonocytic origin of this cell type, which led to the designation "plasmacytoid monocytes." In order to obtain a comprehensive immunophenotype of this cell, we used frozen serial sections of lymph nodes, an indirect immunoperoxidase technique, and a broad panel of well-defined monoclonal antibodies (mAbs). On PTCs, the antigenic density was high for CD4 and CD26 antigens and low for CD2; they furthermore reacted with the mAb OKM5 recognizing an undefined antigen associated with the myelomonocytic lineage and expressed the monocyte-associated antigen CD68. PTCs expressed HLA-A, B, C, HLA-DR, and the HLA-D associated invariant chain (Ii) while HLA-DP antigens were expressed only in low amounts and HLA-DQ antigens were lacking entirely. PTCs further expressed the adhesion molecule CD11c. The absence of detectable transferrin receptor and the proliferation antigen defined by Ki-67 indicated that PTCs were nonproliferating. Other well-defined antigens confined to the T-, B-, and myelomonocyte lineages could not be detected in the target cell population. For us, antigenic equipment is still suggestive of a sessile, terminally differentiated T cell likely to exert a secretory function as yet unknown.

Monoclonal antibody MT1: a marker for Langerhans cell histiocytosis

Langerhans cells and their pathologic counterparts can be identified in paraffin sections using immunohistochemical staining for S-100 protein. This procedure is useful in confirming a diagnosis of Langerhans cell histiocytosis (LCH). However, many other cell types are also positive for S-100 protein. Positive staining for CD1 (Leu 6) supports a diagnosis of LCH, but requires frozen tissue. A panel of antibodies would be desirable in confirming a diagnosis of LCH, particularly if these antibodies could be used on paraffin-embedded material. We studied the pattern of staining for commercially available monoclonal antibodies MT1, MT2, MB2, and LN1, which were originally marketed as lymphocyte markers, using paraffin-embedded tissue sections of cases of LCH. In all 20 cases pathologic Langerhans cells stained positively with MT1 only. Various other S-100 protein-positive lesions were also examined with MT1 and were consistently negative for MT1. Other cutaneous histiocytic and mast cell lesions were positive with MT1, but S-100 protein negative. Our results demonstrate that the monoclonal antibody MT1 serves as an additional marker for LCH and, together with S-100 protein, would make up a diagnostic panel of antibodies for LCH to be used on routine paraffin-embedded sections.

B cell associated monoclonal antibody L26 may occasionally label T cell lymphomas

Monoclonal antibody L26 has been shown to be a very sensitive marker for B lymphocytes in formalin-fixed, paraffin-embedded tissue. Most studies have found that the antibody is also highly specific for B cells, although a few examples of L26-positive T cell lymphoma (TCL) have been reported. We have studied L26 reactivity in 50 TCLs (all previously extensively immunophenotyped on frozen sections) and found positive labelling in 4 cases (3 pleomorphic, medium and large cell type with surface membrane staining; 1 T-anaplastic large cell type with cytoplasmic staining). The finding that L26 may give surface labelling in occasional TCLs (particularly of the pleomorphic, medium and large cell type) indistinguishable from that seen in B cell lymphomas emphasises the importance of always using diagnostic MAbs in combination if the risk of misinterpretation of lymphoma cell lineage is to be minimised.

UCHL1-positive extranodal lymphoma resembling multiple lymphomatous polyposis of the gastrointestinal tract

Histopathologic and immunohistochemical studies were done on paraffin sections from a patient with alimentary tract lymphoma resembling multiple lymphomatous polyposis of the gastrointestinal tract (MLP). Diffuse, but not follicular, proliferation of medium-sized lymphoid cells was noted in the polypoid lesions of the alimentary tract, peripancreatic lymph nodes, spleen, liver, and bone marrow. These cells possessed a T-cell-related antigen (UCHL1), but were negative for the B-cell-related and myeloid cell-related antigens examined. Because neoplastic cells in MLP are usually of B-cell origin, the current case will provide important information on the relation between phenotypes and morphologic patterns of proliferation.

Comparative quality assessment in immunocytochemistry: pilot study of CD15 staining in paraffin wax embedded tissue in Hodgkin's disease

The feasibility of comparative quality assessment studies in immunocytochemistry was examined. The reactions of three CD15 antibodies--anti-Leu M1, DM1, and Tü9--were examined in paraffin wax sections in Hodgkin's disease under a variety of different fixation and pre-treatment conditions, using four immunochemical detection techniques. All three antibodies stained Reed-Sternberg cells, but DM1 could be used at slightly higher dilutions to achieve comparable results. Tissue fixed in formol sublimate showed the most intense staining reactions, and formol saline and neutral buffered formalin gave relatively poor results. Although neuraminidase pre-treatment improved staining, its routine use is probably contraindicated by its high cost. Trypsinisation has some value for sections of tissue fixed in formol saline and neutral buffered formalin. The avidin-biotin complex technique produced the best results, but indirect immunoperoxidase produced acceptable results, is technically easier to perform, and is less expensive. It is concluded that information regarding variations in techniques and commercially available reagents, which may be of use in routine diagnostic histopathology, can be obtained by comparative quality assessment studies of this type.

Molecule detected in formalin fixed tissue by antibodies MT1, DF-T1, and L60 (Leu-22) corresponds to CD43 antigen

Three monoclonal antibodies MT1, L60 (Leu-22), and DF-T1, were reported independently as recognising human T cells in routinely processed, paraffin wax embedded tissue. The present study was performed to compare these three reagents in terms of their immunocytochemical reactions and target molecule(s). On Western blotting of white cell extracts the three antibodies reacted with antigens of the same molecular weight (range 110-160 kilodaltons). Furthermore, their immunocytochemical reactivity with normal human cells, as analysed by two-colour flow cytometry, was essentially identical (labelling of monocytes, most T lymphocytes, and weak reactions with some B cells), and the antibodies gave closely similar reactions on 54 white cell derived neoplasms. To identify the target antigen for these three reagents, antibodies from the Third International Workshop on Leucocyte Antigens were reviewed and it was shown that the Western blotting and immunocytochemical reactions of MT1, L60 (Leu-22), and DF-T1 were identical with those of the reagents which defined the CD43 antigen (also known as leucosialin or sialophorin). Furthermore, all these antibodies reacted with cells transfected with a cDNA clone encoding CD43. It is concluded that antibodies MT1, L60 (Leu-22), and DF-T1 all recognise the heavily glycosylated myeloid/lymphoid associated CD43 antigen.

Immunophenotypic analysis of sinonasal non-Hodgkin's lymphomas

A panel of paraffin effective antibodies recognizing B cells and T cells (LN-2, MB1, L26, MT1, UCHL1, kappa, lambda) was used to characterize the immunophenotypes of 26 sinonasal non-Hodgkin's lymphomas. Seventeen tumors were stage I, five were stage II, one was stage III, and three were stage IV. Nine lymphomas were classified morphologically as large cell, six were large cell immunoblastic, six were small cleaved cell, two were mixed small and large cell, two were small noncleaved cell, and one was lymphoblastic. None were follicular. Twenty-two lymphomas had a B cell immunophenotype, three were T cell neoplasms, and one was immunoreactive only for MT1. This predominance of sinonasal lymphomas with a B cell immunophenotype in patients residing in the United States contrasts with the almost exclusive occurrence of T cell sinonasal lymphomas in Chinese patients living in Hong Kong and Japanese patients residing in regions of Japan that are nonendemic for human T cell leukemia virus-1.

Use of monoclonal antibodies (UCHL1, Ki-B3) against T and B cell antigens in routine paraffin-embedded skin biopsy specimens

Diagnosis and classification of cutaneous lymphoid infiltrates are often hampered by lack of frozen tissue to allow detailed immunophenotyping. Therefore antibodies that recognize antigens resistant to routine tissue processing would be of value. In this study we present a detailed analysis of two such antibodies against CD45R antigens, UCHL1 and Ki-B3, that detect predominantly T or B cells, respectively. Tumor cells in 125 cases of various nonlymphatic skin tumors did not react with either UCHL1 or Ki-B3. Examination of 85 biopsy specimens from 13 different inflammatory skin diseases demonstrates that most reactive T cells in the skin carry the UCHL1 antigen, as controlled by simultaneous immunophenotyping in frozen tissue. With few exceptions, UCHL1 also detected the tumor cells in 28 cases of cutaneous malignant T cell lymphomas. In contrast, Ki-B3 failed to detect tumor cells in seven of eight cases of malignant B cell lymphomas of the skin.

Diagnostic fine needle core biopsy of deep lymph nodes for the diagnosis of lymphoma in patients unfit for surgery

The use of a technique for safe percutaneous fine needle biopsy of inaccessible lymph nodes is described. In a prospective study of 24 patients, including five cases positive for the human immunodeficiency virus (HIV), this technique was used to provide diagnostic material. A firm diagnosis was made in 21 cases; four cases of Hodgkin's disease, 14 non-Hodgkin's lymphomas, one case of Kaposi's sarcoma, one case of mycobacterial infection, and one which showed the features of persistent generalized lymphadenopathy (PGL). In the cases of lymphoma, available serial sections allowed characterization of the tumour with immunocytochemistry. In three cases, no diagnosis could be made, with one of these requiring a subsequent open biopsy. Percutaneous fine needle biospy is ideal for patients unfit or unsuitable for general anaesthesia or surgery. The biopsy obtained gives the pathologist sufficient tissue for an accurate diagnosis in the majority of cases. The preservation of architecture and multiple sections available are advantages over fine needle aspiration.

Lymphoma phenotyping in formalin-fixed and paraffin wax-embedded tissues: II. Profiles of reactivity in the various tumour types

Recently, monoclonal antibodies capable of phenotyping malignant lymphomas in routinely fixed and processed tissue have become available. Some of these reagents identify lineage-restricted variants of the leucocyte common molecule, whereas others identify unique fixation-resistant epitopes on lymphoid cells, some of which are shared by non-lymphoid tissues. A new generation of antibodies recognizing 'classical' leucocyte antigens such as CD3 are also emerging. Refinements in antigen detection systems, especially for immunoglobulin recognition, combined with these new reagents promise to improve the accuracy of lymphoma diagnosis in routine histopathology. These new antibodies are reviewed, and their limitations, cross reactivities and profiles of staining in lymphoreticular disease are discussed. A strategy for their optimal use is proposed.

A retrospective study of follicular lymphomas

Sixty-four cases of follicular lymphoma followed-up for 10 years have been studied. The influence of age, sex, histological appearance, immunophenotype and T-cell content on prognosis has been examined. Initial evaluation indicated that increasing age, relatively low numbers of intrafollicular T-cells and absence of mantle zones around the neoplastic follicles were associated significantly with mortality. Multiple regression analysis with adjustment for age and sex was performed and the only significant variable was then found to be the histological grade.

Primary gastric malignant lymphoma. A morphological and immunohistochemical study of 38 cases

Thirty-eight cases of primary gastric malignant lymphoma were studied morphologically and immunohistochemically. The Working Formulation was used for classification of non-Hodgkin's lymphoma (1). The results indicated that 37 cases were non-Hodgkin's lymphoma while the remaining case was Hodgkin's disease. Thirty-three cases (89%) of non-Hodgkin's lymphoma were considered to be of B cell origin and 2 cases (5%) of histiocytic origin. No case was considered to be of T cell origin. We suggest that the majority of primary gastric malignant lymphomas are derived from follicular center cells, and that gastric plasmacytoma is not as rare as previously described.

Immunoreactive cytokeratins in plasmacytomas

Fourteen plasma cell tumours, including examples of solitary plasmacytoma and multiple myeloma, were studied with a panel of antibodies reactive in formalin-fixed, paraffin wax-embedded tissue. Each case showed immunoglobulin light chain restriction. Five tumours were reactive with antibodies to cytokeratin. Of these five cases, four were negative with antibodies to leucocyte common antigen and only one was weakly positive. Anti-cytokeratin reactivity by plasma cell tumours is more common than was originally anticipated and represents an important diagnostic pitfall.

Primary extranodal non-Hodgkin's lymphoma of the oral region

Seventy cases (47M, 23F) of primary extranodal non-Hodgkin's lymphoma of the oral region were studied to determine tumor characteristics. The most frequent disease sites were the palate (21 cases), gingiva (17 cases) and parotid gland (13 cases). Each lymphoma was classified according to the criteria of the Working Formulation for Clinical Usage. Only 5.7% of cases were follicular lymphomas while diffuse lymphomas had a high incidence. Histologic subtypes included small lymphocytic (1%), small cleaved cell (7%), mixed small and large cell (20%), large cell (43%), large cell, immunoblastic (17%), lymphoblastic (9%) and small non-cleaved cell lymphoma (3%). Immunologic study utilizing the avidin-biotinylated horseradish peroxidase complex (ABC) technique demonstrated the presence of intracytoplasmic monoclonal immunoglobulin in 24 (34%) of the suggested B-cell lymphoma cases; 20 tumors (28%) were classified as T-cell lymphoma based on a positive reaction for mouse monoclonal antibody (UCHL-1) to T-cell related membrane antigen; 11 tumors (16%) contained intracytoplasmic alpha 1-antitrypsin, suggesting true histiocytic lymphoma; 15 tumors (22%) did not contain immunoglobulin, UCHL-1 or alpha 1-antitrypsin positive cells and showed no definite characteristics.

Non-Hodgkin's lymphoma involving the brain. Diagnostic usefulness of stereotactic needle biopsy in combination with paraffin-section immunohistochemistry

A stereotactic needle biopsy was examined for applicability in diagnosing brain non-Hodgkin's lymphoma (NHL), because the procedure is far less aggressive than biopsy by open surgery. Formalin-fixed materials including four stereotactic specimens were available from nine patients with brain NHL. In addition to routine histopathology and histochemistry, paraffin-section immunohistochemistry was performed using a panel of monoclonal antibodies suited to such sections. Although several histopathological features characteristic of brain NHL could not be evaluated in three of the four stereotactic specimens owing to the small size of the specimens and partial invasion by lymphoma cells, the lesions in all cases could be characterised by immunohistochemistry. Examination for cytoplasmic immunoglobulin (cIg) was also performed, but specific identification of cIg was difficult in five cases because of diffuse background staining and passive diffusion of plasma protein into the cells during tissue processing. A review of the literature indicates the technical difficulty in cIg staining, since the incidence of cIg-positive cases in an individual study varied considerably, and lymphoma cells in 15 of 128 cIg-positive brain NHL cases have been reported to possess both light chains. From these findings, together with the relative difficulty in obtaining fresh tissues for study, it is concluded that, when the specimens are to be examined by paraffin-section immunohistochemistry using the above monoclonal antibodies, stereotactic needle biopsy is a useful, less aggressive method for diagnosing brain NHL.

Applications of immunocytochemistry to diagnostic cytopathology

Immunohistochemical technique is now successfully applied to the cytologic materials. This review article describes details of staining procedures for immunocytochemistry at both light and electron microscopic levels. The clinical application of the technique includes aspiration biopsy cytology for breast lesions, thyroid lesions, lymph nodes, the nervous system, and others. The establishment of carcinoma cells in the body fluid by the demonstration of carcinoembyronic antigen (CEA) and the establishment of specific diagnoses in small-cell or large-cell anaplastic tumors by immunocytochemistry warrants special emphasis.

Monoclonal antibody MB2: a potential marker for Ewing's sarcoma and primitive neuroectodermal tumor

The small round-cell tumors of childhood present difficulties in diagnosis when differentiation is not apparent. Immunohistochemistry is helpful; however, the only antigen consistently detected in Ewing's sarcoma is vimentin, which may also be detected in the other types of small-cell neoplasms. The monoclonal antibody (MAb) MB2 is marketed as a B-lymphocyte marker that can be used on paraffin-embedded tissue. To determine its specificity, we performed immunohistochemical staining on pediatric tumors with MB2. These included 55 cases of small round-cell tumors (lymphomas, Ewing's sarcoma, peripheral primitive neuroectodermal tumors [PNET], neuroblastomas, rhabdomyosarcomas, and nephroblastomas). MB2 positivity was detected in all B-cell lymphomas and in seven of nine cases of Ewing's sarcoma and three PNET. In neuroblastomas only differentiating ganglion cells were positive. In rhabdomyosarcomas only large rhabdomyoblasts were positive. Blastema of nephroblastomas was negative. Thus, in cases of poorly differentiated small round-cell tumors, MB2 was positive in all B-cell lymphomas, most Ewing's sarcomas and all cases of PNET. Lymphomas were distinguished by staining for leukocyte-common antigen and PNET by neuron-specific enolase. Therefore, the addition of MB2 to a discrete panel of antibodies may prove useful in the diagnosis of Ewing's sarcoma and PNET.