Malignant lymphoma of true histiocytic (monocyte/macrophage) origin

Since the advent of the newer classifications of non-Hodgkin's lymphoma and the realization that the majority of tumors classified as histiocytic under the Rappaport classification were in fact of lymphocytic origin, there have been remarkably few reports of true histiocytic (monocyte/macrophage) tumors and it has been suggested by some that such tumors should not be considered as a variety of malignant lymphoma. This article describes five patients with malignant lymphoma of neither B- or T-lymphocyte origin in whom the malignant cells could be characterised immunologically, cytochemically, and immunohistochemically as of true histiocytic derivation. The cases showed considerable morphologic diversity but there were shared characteristics at both light microscopic and ultrastructural levels. Positive immunohistochemical staining for alpha 1-antitrypsin was the single most useful criterion in classifying these tumors. Without the use of special techniques there were no clinical or pathologic features that reliably distinguished these cases from non-Hodgkin's lymphomas of lymphocytic derivation. Tumors of histiocytic origin are, therefore, inevitably being included among the non-Hodgkin's lymphomas and are most appropriately classified as such. Identification of histiocytic lymphomas should be encouraged so prognosis and optimum treatment can be established.     

Morphology and immunohistochemistry of true histiocytic lymphoma--report of 4 cases

True histiocytic lymphoma (THL) is a rare malignancy of histiocyte. It is difficult to diagnose by light microscopy alone. In this paper, 4 cases of THL were reported basing on light and electron microscopic examination, and immunohistochemical study. Histiocytic lymphoma was of Langerhans cell origin in one case and of interdigitating reticulum cell origin in the other. The other 2 patients probably belonged to neoplasm of macrophage or dendritic reticulum cell origin. The differential diagnosis between the true histiocytic lymphoma and other tumors or diseases was briefly discussed.     

Immunoreactivity of granular cell lesions of skin, mucosa, and jaw

Granular cell lesions from many different sites share similar light and electron microscopic features. Immunologically, however, these lesions do not appear to be a homogenous group. This study determines the extent of immunologic heterogeneity of granular cell lesions from a wide variety of sites in skin, mucosa, and jaw. Thirty-one granular cell lesions (26 granular cell tumors [GCT] and five other granular cell lesions) from 18 different sites were evaluated immunohistochemically for keratins, vimentin, desmin, muscle actin, ACT, HLA-DR, and S-100 protein. Paraffin-embedded sections were utilized with an avidin-biotin complex immunoperoxidase technique. Except for ameloblastomas, all lesions were negative for keratin and positive for vimentin. All lesions were negative for desmin and actin. Positive ACT reactivity was found in one of seven GCT of tongue, a colonic lesion, a nose lesion, and a granular cell ameloblastic fibroma. All lesions were positive for HLA-DR except a few in which fixation appeared inadequate. S-100 immunoreactivity was found in all lesions except the congenital epulis, a GCT of the skin of the nose, a colonic lesion, and the odontogenic tumors. The antigenic profile of GCT of skin and mucosa is consistent with Schwann cell origin. However, some GCT and other granular cell lesions appear to be derived from macrophages, epithelial cells, or other cells. The expression of HLA-DR by granular cells is believed to be unrelated to cellular origin but rather to some common immunologic function.     

Langerhans' cells and macrophages in eosinophilic granuloma. An enzyme-histochemical, enzyme-cytochemical, and ultrastructural study

Biopsy material of six patients with eosinophilic granuloma (EG) was investigated by electron microscopic and enzyme-histochemical methods for acid phosphatase (AcP), leucyl-beta-naphthylamidase (LA), adenosine triphosphatase, and alpha-naphthyl-acetate esterase (NE). Paraplast sections were used for demonstration of lysozyme with an immunoperoxidase method. Results of staining for these different enzymes suggested the existence of two separate sets of histiocytic cells: one type with "dot-like" AcP staining and negative for NE and lysozyme; and the other with diffuse AcP staining, positive for NE and lysozyme, and often showing signs of phagocytosis. The first type presumably represented Langerhans' cells and also often showed positive staining for LA. Macrophages were generally negative for LA. Electron microscopic study confirmed the impression gained from enzyme-histochemical studies. No intermediate cell types between Langerhans' cells and genuine macrophages were seen. From these results it is concluded that in EG no transformation exists between Langerhans' cells and macrophages. The latter are presumably of reactive nature.     

Malignant histiocytosis and related tumors. A clinicopathologic study of 42 cases using cytological, histochemical and ultrastructural parameters

Light and electron microscopical, immunohistochemical and clinical characteristics in 42 cases of malignant neoplasms, arising from true histiocytes, are described. These were separated in a lymphoma-like subtype, called true histiocytic lymphoma (29 patients) and a disseminated variant, called malignant histiocytosis (9 patients). In addition 4 related histiocytic tumors are discussed, including 2 tumors arising from interdigitating cells. Sinus pattern and cytologic features, especially 'window' nuclei, are emphasized as diagnostic criteria. Erythrophagocytosis was not a constant finding. Electron microscopic features, presence of acid phosphatase, acid alpha-naphthylacetate esterase, lysozyme, alpha 1-antitrypsin, alpha 1-antichymotrypsin, Ia-antigen and absence of B- and T-cell markers, were important in establishing the histiocytic nature or excluding a non-histiocytic tumor. A distinct male predominance existed (male:female = 2.5:1) with a higher relapse free period in females (p = 0.032). A high number of mitotic figures appeared to be a favourable sign, p = 0.020 and 0.019, for remission rate and relapse free period respectively. The degree of cell differentiation and the immunohistochemical pattern did not show a correlation with remission and relapse free period. Extranodal involvement and the presence of short profiles of endoplasmic reticulum were prognostically unfavourable signs. True histiocytic lymphomas showed a higher remission rate (p = 0.041) and relapse-free period (p = 0.017) than malignant histiocytosis.     

Plasma cell granuloma of the lung (inflammatory pseudotumor)

A case of plasma cell granuloma (PCG) of the lung in a 54-year old man is reported. PCG is a rare benign lesion that usually presents as a solitary nodule in the lung (coin lesion) at routine X-ray examination. Microscopically it consists of a granulomatous tissue where the major components are mature plasma cells. The immunohistochemical demonstration of polyclonality of plasma cells, excluding the diagnosis of plasmacytoma, confirms the inflammatory pseudotumoral nature of this lesion, although the etiology remains obscure. The presence of lymphocytes, histiocytes, macrophages, blood vessels with prominent endothelial cells and peripheral sclero-hyalinized connective tissue may pose problems in the differential diagnosis with sclerosing hemangioma, pseudolymphoma, nodular amyloidosis, pulmonary hyalinizing granuloma, chronic abscess and neoplasms of true histiocytic origin. The term inflammatory pseudotumor is preferable in describing this type of lesion.     

An unusual organoid tumor. Alveolar soft part sarcoma or paraganglioma?

The histogenesis of alveolar soft part sarcoma (ASPS) is a subject of continued debate. Although many recent reports suggest a muscle origin, others advocate a neuroendocrine derivation. A tumor in the chest wall of a 16-year-old woman was diagnosed and treated as ASPS. The light microscopic, electron microscopic, and immunohistochemical findings showed features of both ASPS and paraganglioma. In addition, this lesion was positive for antibody to glucagon, a characteristic of neither ASPS nor paraganglioma, although seen in a few gangliocytic paragangliomas. This case demonstrates the need for continued inquiry into the histogenesis of ASPS.     

Acute myelomomocytic leukemia terminating in histiocytic medullary reticulosis: cytochemical, cytogenetic and electron microscopic studies.

A case of acute myelomonocytic leukemia terminating in histiocytic medullary reticulosis is reported. The evolution of a single cellular clone presenting with progressive change of the morphological features of the leukemic cells towards more anaplastic elements endowed with prominent phagocytic properties is suggested on the basis of both cytochemical and chromosomal data. The histiocytic nature of the malignant proliferating cells and platelet phagocytosis has been confirmed by electron microscopic investigation. The main pathogenetic explanations of the evolutionary patterns of the disease are discussed with relation to: a) involvement of a common stem cell giving rise to different proliferative patterns of cells in a multiphasic sequence; b) release of dysplastic platelets and defective erythrocytes with massive sequestration by histioid phagocytic cells; and c) coexistence of two different disorders.     

Nodular lymphocytic lymphoma eventuating into diffuse histiocytic lymphoma: immunoperoxidase demonstration of monoclonality.

The patient described here had a nodular, poorly differentiated lymphocytic lymphoma associated with a serum monoclonal protein, IgG lambda. Following a three year period of radiation-induced clinical remission she developed generalized diffuse histiocytic lymphoma. Direct immunoperoxidase staining of the tissue sections demonstrated that the neoplastic cells of each biopsy only contained IgG lambda immunoglobulin, identical to the serum monoclonal protein. This is presumptive evidence that these two histopathologically distinctive malignant lymphomas, occurring consecutively in the same patient, were responsible for the synthesis and secretion of the same serum M component. This strongly suggests that both lymphoid neoplasms arose from the same malignant clone. The results 1) confirm the light microscopic observation that nodular lymphocytic lymphoma may progress to diffuse histiocytic lymphoma and 2) offer further evidence that histiocytic lymphomas arising in patients with previous B cell malignancies are most probably related to the original B cell proliferation and do not represent the emergence of a second, separate malignant clone.     

皮肤真性组织细胞性淋巴瘤的诊断与误诊分析

目的 探讨右大腿皮肤组织细胞性恶性淋巴瘤的诊断、误诊原因及预防对策。方法 对1例皮肤组织细胞性淋巴瘤的标本，采用10％的福尔马林固定，石蜡切片，HE、网状纤维染色及多种免疫组化染色，光镜观察、会诊及病理读片会讨论。结果 临床因早期表现为局部单发肿块，皮肤改变不明显而误诊为皮肤纤维瘤，病理则因组织学上既象淋巴瘤样细胞弥漫分布又有瘤细胞互相粘着不松散而似癌细胞巢，且瘤细胞核大，核仁明显又似恶性黑色素瘤，凭皿切片难以诊断，免疫组化及会诊结果为皮肤组织细胞性恶性淋巴瘤。结论 原发于皮肤的组织细胞性恶性淋巴瘤非常少见。组织学上注意与蕈样霉菌病、美克耳细胞癌、恶性黑色素瘤、恶性组织细胞增生症等鉴别。免疫组化不支持上述病变时要想到本病的可能。误诊的主要原因是早期临床表现不具有特征性，肿瘤发病部位及类型罕见，临床及病理对此类型淋巴瘤认识不深，未能及时进行免疫组化检查。     

Immunohistochemical distribution of S-100 protein in tumors and tumor-like lesions of bone and cartilage

Various tumors and tumor-like lesions of bone and cartilage were examined for S-100 protein using the avidine-biotin-peroxidase complex (ABC) immunostaining method. The most intense reactivity for S-100 protein was found in well-differentiated chondrocytes of enchondromas, osteochondromas and chondrosarcomas, and in normal epiphyseal cartilage. S-100 protein was positive in both polygonal stromal cells and chondrocytes of chondroblastomas and in chondrocytes of mesenchymal chondrosarcoma. In osteosarcomas not only chondroblastic areas but also osteoblastic areas showed positive cells. Reticulum histiocytic cells of eosinophilic granulomas and chordoma cells were positive for S-100 protein. The study yielded three main conclusions: (1) S-100 protein could be the marker for tumors of cartilaginous origin and differentiation, notochord origin, and T-zone histiocyte origin; (2) chondroblastoma can be distinguished from other histologically confusing giant cell lesions by using ABC to detect S-100 protein; and (3) S-100 protein has some relationship with tumoral calcification not only in cartilaginous tumors but also in osteosarcoma.     

Expression of the BLA antigen, defined by the monoclonal 38.13 antibody, on Burkitt lymphoma lines, lymphoblastoid cell lines, their hybrids and other B-cell lymphomas and leukemias

The BLA expression of eight Burkitt lymphoma lines was high, whereas it was negative in four, including the two IgG producers tested. Most lymphoblastoid cell lines (LCL) of normal origin had only a low percentage of positive cells, not significantly above background, although a few had up to 30% positives. EBV conversion of the EBV-negative Burkitt lymphoma line Ramos destabilized the high BLA expression, leading to a decrease in the average number of positive cells in the majority of the converted sublines in parallel with considerable fluctuation in antigen expression within each subline. Our group has previously shown that EBV-conversion of Ramos cells can induce certain differentiation steps (Spira et al., 1981 a). EBV-converted sublines of another EBV-negative Burkitt lymphoma, BJAB, showed a much greater stability previously and remained unchanged with regard to BLA expression in our present experiments. Eight T-cell leukemias, three myeloid leukemia lines and two diffuse histiocytic lymphomas were negative for BLA, whereas two myeloma lines were 30-40% positive. A histiocytic tumor had marginal reactions. Hybrids derived from the fusion of high with low BLA-reactive parental lines showed all three possible patterns (high, intermediate and low), provided that B-cell lines were fused with each other. Fusion of two Burkitt lymphoma lines with the K562 erythroleukemia line led to the extinction of BLA expression, as well as to the eclipse of other B-cell markers. B-lymphoma and leukemia (CLL) cells harvested directly from the patient showed a heterogeneous reactivity pattern. Strong to intermediate BLA expression was found among CLL cells and in most histological groups of B-CLL lymphomas except the centroblastic group (3/3 negatives). IgG-expressing follicular lymphomas were less reactive than IgM +/- IgD lymphomas of the same group. Immunocytomas were also low-reactive. BLA can be thus expressed on a variety of B-cell neoplasms; the degree of its expression appears to be related to the stage of differentiation.     

Infrequent activation of K-ras, H-ras, and other oncogenes in hepatocellular neoplasms initiated by methyl(acetoxymethyl)nitrosamine, a methylating agent, and promoted by phenobarbital in F344 rats

Fischer 344/Ncr rats of both sexes were subjected to partial hepatectomy and then initiated 21-24 h later by a single injection of methyl(acetoxymethyl)nitrosamine at 0.1 mmol/kg body weight via the portal vein. Beginning 3 weeks later, development of hepatocellular neoplasms in initiated rats was promoted by feeding 0.05% phenobarbital (PB) in the diet. Not only intrahepatic lesions but also a variety of extrahepatic tumors were induced. High-molecular-weight DNAs were prepared from 67 samples of grossly normal liver containing multiple preneoplastic foci/areas of microscopic dimensions, 137 hepatocellular adenomas (nodules), 93 hepatocellular carcinomas (HCC), 10 cholangiomas, and 25 extrahepatic tumors in 95 rats and tested for transforming activity in the NIH 3T3 transfection assay. DNA preparations from 7 of 93 HCCs, 2 of 10 cholangiomas, 2 of 137 nodules, 1 histiocytic sarcoma, and 1 thyroid carcinoma were positive in the transfection assay. Southern blot analysis showed that NIH 3T3 transformants induced by DNA from 5 HCCs, 1 hepatocellular adenoma, 1 cholangioma, 1 histiocytic sarcoma, and 1 thyroid carcinoma contained an activated K-ras gene of rat origin. Rat-derived H-ras was identified in transformants from 2 additional HCCs and rat c-raf from 1 hepatocellular adenoma. The transforming gene from one cholangioma showed no sequence homology to the ras genes, neu, or c-raf. Immunoprecipitation analysis of ras Mr 21,000 protein in 11 transformants indicated that, based upon protein electrophoretic mobilities, activation of the ras genes consistently resulted from mutations in codon 12 of these genes. Selective oligonucleotide analysis revealed that a G----A transition in the second base of codon 12 of K-ras was present in the 9 K-ras-positive transformants and also in DNAs prepared from the original tumors. In contrast, oligonucleotide hybridization experiments with DNAs from 35 hepatocellular tumors that were negative in transfection assays revealed the presence of mutant K-ras in 1 of 15 HCCs; no mutation could be detected in 20 transfection-negative adenomas. The infrequency of detection of a specific oncogene, more frequent detection of oncogenes in malignant tumors, and failure to observe activated oncogenes in preneoplastic lesions suggest that activation of ras oncogenes may occur as a late and infrequent event in the evolution of some rat hepatocellular neoplasms and that mutation of a specific ras locus is not an obligatory early event in the genesis of these neoplasms.     

Diagnostic significance of histiocyte-related markers in malignant histiocytosis and true histiocytic lymphoma

Interrelationships of immunologic and enzymatic markers of histiocytes have been studied in malignant neoplasms of histiocytic/monocytic origin and in differential diagnostically relevant, large cell non-Hodgkin's lymphomas. Cryostat sections required for demonstrating cell surface antigens by monoclonal antibodies are inadequate for studying cellular detail, enzymatic maturation by alpha-naphthyl acetate esterase (ANAE), and demonstrating the classical cytoplasmic markers of histiocytes like lysozyme, alpha-1-antitrypsin (AT), and alpha-1-antichymotrypsin (ACT). These markers have been compared in gently fixed and vacuum paraffin-embedded material. The reactivity for monoclonal anti-human monocyte 1 (Mo 1) has also been preserved by this method. Malignant histiocytosis (MH) is characterized by a heterogeneous cell population. The mature, ANAE-positive cells with macrophage morphology usually show a diffuse cytoplasmic positivity for AT and ACT. Lysozyme is moderately positive to negative in these cells, but it is more efficient than these markers in revealing smaller cells resembling monocytes by focal positivity in the cytoplasm. The expression of Factor XIIIa (F-XIIIa) is connected with the phagocytic activation of histiocytic cells. F-XIIIa positive cells usually form a minority of the neoplastic population in MH, but the large cytophagocytic marcophages are invariably positive. Reactive macrophages in large cell non-Hodgkin's lymphomas are characterized by a coexpression of ANAE, AT, ACT, lysozyme, F-XIIIa and Mo 1. Typical cases of true histiocytic lymphoma (THL) are made up of a homogeneous population showing the above mature, phagocytizing phenotype. In MH, Mo 1 and ANAE recognize different subpopulations. The reciprocal relation of these markers is an abnormal phenotypic feature. The results presented in this article prove the diagnostic value of ANAE and lysozyme in confirming the histiocytic differentiation of malignant cells. Monoclonal anti-human monocyte 1 is useful for identifying the immature component in MH. Factor XIIIa can be considered a functional marker of mature phagocytic histiocytes and an aid in the diagnosis of THL.     

Non-Hodgkin's lymphomas: an ultrastructural study correlating morphology with immunologic cell type.

Ultrastructural studies were performed on 40 B-cell and 14 T-cell lymphomas of non-Hodgkin's type (NHL). Most B-cell lymphomas were comprised of neoplastic cells with morphologic features compatible with a follicular center cell origin. Dendritic reticulum cells and their desmosome-associated processes, characteristic of germinal centers, were observed in all 11 cases of nodular poorly differentiated lymphocytic lymphoma and in one of two cases of nodular "histiocytic" lymphoma, but were not identified in the lymphomas with a diffuse growth pattern. Desmosomes were observed between dendritic reticulum cells and were not found between lymphoid cells. Large neoplastic cells comprising lymphomas of "histiocytic," mixed lymphocytic "histiocytic," and "undifferentiated" types were characterized ultrastructurally and immunologically as lymphoid cells. Malignant lymphomas of well and moderately well differentiated lymphocytic types (7 cases) revealed B-cell markers, and represented a distinct homogenous group of neoplasms, with electron microscopic features most closely resembling follicular cuff lymphocytes. T-cell malignancies included lymphoblastic lymphomas (3 cases), large cell ("histiocytic") lymphomas (4 cases), lymphoepithelioid cell ("Lennert's") lymphomas (2 cases), mycosis fungoides (3 cases) and diffuse poorly differentiated lymphocytic lymphomas (2 cases). A consistent finding in the T-cell proliferations was the presence of small and/or large lymphoid cells with extremely irregular and/or convoluted nuclei, which occurred in varying proportions and with variable degrees of nuclear complexity. The nuclear irregularity evident in the neoplastic T cells was distinguishable from that observed for lymphoid cells of B-cell lymphomas. In comparing the cytoplasmic features of the T- and B-cell neoplasms ultrastructurally, the only distinguishing feature was the presence of well developed granular endoplasmic reticulum with dilated cisternae, i.e., plasmacytoid features, predictive of a B cell origin.     

Biology of the human malignant lymphomas. IV. Functional characterization of ten diffuse histiocytic lymphoma cell lines.

Ten consecutive diffuse histiocytic lymphoma (DHL) cell lines established in our laboratory were studied for the presence of Epstein-Barr virus (EBV) genomes, lysozyme, nonspecific esterase and other cytochemical reactions, phagocytic activity, cytoplasmic immunoglobulin light and heavy chains, and surface receptors to sheep erythrocytes, complement, and the Fc fragment of immunoglobulin. In agreement with previous studies performed on biopsy specimens, our results indicate that the diffuse histiocytic lymphomas, as a histopathologic entity, represent a heterogeneous group of neoplasms, the majority of which are B-lymphocyte in origin. The cell lines appear to fall into three categories based on the following criteria: 1) presence of monoclonal cytoplasmic immunoglobulins (B-lymphocytic type, 6/10 cell lines); 2) presence of non-specific esterase, phagocytic activity, and/or lysozyme (histiocytic type, 2/10 cell lines); and 3) absence of all lymphoid and histiocytic cell characteristics (null cell type, 2/10 cell lines). Despite the fact that many of the lymphoma patients had positive serologies to EBV antigens, all of the DHL cell lines were negative for the presence of EBV genomes. Both of the two B-lymphocytic type and one of the two histiocytic type lines tested were susceptible to infection with EBV, as indicated by synthesis of early antigen and also, in a small proportion of the infected cells, of viral capsid antigen. These prototypic DHL cell lines may permit the development of new criteria for the differential diagnosis and treatment of this highly malignant and diverse group of lymphomas.     

A T-cell neoplasia showing clinicopathologic features of malignant histiocytosis with novel chromosomal abnormalities and N-ras mutation

Malignant histiocytosis (MH) is a distinct disease entity defined clinically and morphologically. However, the neoplastic origin of MH is not well established. The authors report a 26-year-old woman who showed the typical clinicopathologic features of so-called MH. Cytogenetic and molecular genetic examinations were performed in addition to the morphologic and immunologic approach. The expression of CD2 and T-cell receptor gene rearrangements indicated the T-cell origin of this case. CD30, which is positive for anaplastic large cell lymphoma (Ki-1 lymphoma), was not expressed. The cytogenetic study revealed a clonal chromosome abnormality involving 3q25, 6p21, 11p15, and 11q21. An N-ras point mutation within codon 12 (GGT----GCT) was also detected. These finding indicate that MH defined clinically and morphologically is not a tumor of true histiocytic origin and that it should be reclassified on the basis of immunologic, cytogenetic, and molecular genetic data.     

Primary intracranial histiocytic lymphoma with Langerhans' granules. A light microscopic and ultrastructural study

An intracranial tumor classified as a histiocytic lymphoma was studied with light and electron microscopic examination and immunocytochemical methods. The characteristics of the malignant mononuclear phagocyte cells are described. The presence of some cells containing Langerhans' granules suggests differentiation towards a specialized cell of the mononuclear phagocyte system: the Langerhans' cell.     

Primary gastrointestinal lymphomas: a classification of 66 cases.

Using routine histology, resin embedded sections and immunohistochemical techniques on formalin-fixed, paraffin processed tissue, 66 cases of primary gastrointestinal lymphoma have been classified. This study necessitated the development of reliable criteria to separate lymphomas of true histiocytic origin from those of lymphocytic origin. Among the morphologic properties of malignant histiocytes were complex pleomorphic nuclei, abundant well delineated cytoplasm and phagocytosis. These cells were shown to contain all major immunoglobulin chains, C3, lysozyme and in some cases alpha 1 antitrypsin. Malignant lymphomas derived from histiocytes could be divided into two groups: malignant histiocytosis of the intestine (MHI), a recently described diffuse pleomorphic lymphoma associated with villous atrophy of the small intestine, and histiocytic lymphoma (HL) which forms solid tumor masses in a similar manner to lymphocyte derived tumors. Immunohistochemical studies of lymphocyte derived tumors were negative apart from one case with plasmacytoid differentiation. Of the 66 cases, 50% were of histiocytic origin (33% MHI, 17% HL) and 41% of lymphocyte origin, there was one case of Hodgkin's disease and five cases were unclassified. The role of the histiocyte in gastrointestinal mucosa deserves further study.     

Phenotypic expression of non-Hodgkin's lymphomas in China

Monoclonal antibodies were used to label malignant lymphomas obtained from 57 patients. On the basis of morphologic criteria, 18 lymphomas were the B-cell type, 10 were the T-cell type, and 6 were histiocytic; for 23 the type could not be determined. After monoclonal antibody labeling, 18 lymphomas of B-cell lineage were confirmed, 16 of the T-cell type were demonstrated, 6 were true histiocytic, and 17 were the null cell (non-T, non-B) type. Of the 16 lymphomas of T-cell lineage, 6 were lymphoblastic and 10 were the peripheral type. The percentages of cell types in the non-Hodgkin's lymphomas were as follows: B-cell, 31.5%; T-cell, 28%; null cell, 29%; and histiocytic, 10%. Of the 16 lymphomas of T-cell origin, 15 belonged to helper T-cell subsets (Leu1+, Leu4+, and Leu3a+), and the la marker was positive in all 16. Of the 18 B-cell lymphomas, 14 were kappa-positive and 4 were lambda-positive. Eleven were both B1- and kappa-positive, and 1 was kappa-positive but B1-negative. In the 4 cases that were lambda-positive, 2 were both lambda- and B1-positive. The results indicate that Leu4, Leu2a, Leu3a, and B1 are the most important markers to differentiate T-cell and B-cell lymphomas for pathologic classification. The findings also show a higher percentage of T-cell neoplasm in China as compared to that in Western countries.