DISTRIBUTION OF HNK-1+ CELLS IN MALIGNANT LYMPHOMAS

HNK-1, a murine monoclonal antibody, is known to react with most of the natural killer (NK) and killer (K) cells in peripheral blood. Cells reacting with this antibody (HNK-1⁺ cells) were studied on tissue sections of ninety two cases of malignant lymphomas (MLs) by using immunoperoxidase technique, in an attempt to elucidate the role of this type of cells in MLs. Follicular lymphomas were found to be highly infiltrated with HNK-1⁺ cells. The mode of infiltration in follicular lymphomas is just like in normal germinal centers. Many cases of diffuse lymphomas with cleaved nuclei, indicative of diffuse B-cell lymphomas of follicular center cell origin, as well as diffuse ML with heavy fibrosis (sclerosis) or histiocytic reaction, were also found to be infiltrated with abundant HNK-1+ cells. Meanwhile, other types of B-cell ML and all types of T-cell ML, as well as Hodgkin's disease, were shown to be very poor in HNK-1⁺ cell reaction. From a prognostic viewpoint, the low grade malignancy group in the NCI Working Formulation or Kiel Classification was found to be infiltrated with significantly much more HNK-1⁺ cells as compared to the high grade malignancy group. The significance of these findings are discussed, with the stress on the possible suppressive function of HNK-1+ cells on proliferation and differentiation of follicular center cell type B-cell MLs. ACTA PATHOL. JPN. 35: 339–350, 1985.     

Immunohistologic characterization of two malignant lymphomas of germinal center type (centroblastic/centrocytic and centrocytic) with monoclonal antibodies. Follicular and diffuse lymphomas of small-cleaved-cell type are related but distinct entities

The relationship between follicular lymphomas and diffuse lymphomas of small-cleaved-cell type was investigated with the use of a panel of antibodies against B-cell differentiation antigens. Follicular lymphomas, regardless of histologic subtype, were immunologically homogeneous: Ig+ B1+ B2+ CALLA+ Ia+. Two cases were Ig-negative, and 4 were CALLA-negative. Diffuse small-cleaved-cell (centrocytic) lymphomas were more heterogeneous. The majority were Ig+ B1+ B2+ Ia+ T1+ CALLA-. A minority were B2-negative, T1-negative, or CALLA-positive. An increased frequency of Ig heavy chain class switching and loss of T1 antigen suggest that follicular lymphomas are at a later stage of differentiation than most centrocytic lymphomas. The differences in immunologic phenotype provide further justification for a classification that distinguishes between follicular and diffuse lymphomas of small-cleaved-cell types. The expression of Ig, Ia, B1, and B2 on neoplastic follicular center cells correlates with expression of these antigens on normal B cells. In addition, anti-B2 appears to stain a nonlymphoid dendritic cell present in normal germinal centers and in both follicular and diffuse germinal center cell lymphomas in this study. In follicular lymphomas, the dendritic pattern was similar to that of normal follicles, while in centrocytic lymphomas a more irregular dendritic pattern was seen. Dendritic staining was seen in both nodal and extranodal lymphomas, suggesting that these nonlymphoid cells either migrate with neoplastic B cells or are present in a variety of normal tissues.     

Expression of p63 in reactive hyperplasias and malignant lymphomas

p63 is a recently described p53 homologue. It is involved in survival and differentiation of reserve/stem cells in epithelia. To obtain new insights into the role of p63 in malignant lymphomas (MLs), immunohistochemical staining for p63 and p53 was performed in 126 cases of MLs. p63 was expressed in 38 cases of MLs (30.2%) including 32/61 cases (52.5%) of diffuse large B-cell lymphoma (DLBCL), 1/8 cases (12.5%) of precursor T-lymphoblastic lymphoma (T-LBL), 4/14 cases (28.6%) of follicular lymphoma, 1/6 cases (16.7%) of T/NK cell lymphoma. Among p63 positive cases, p63 was strongly expressed in 15/32 cases of DLBCL and 1/1 case of T-LBL. p63 was not expressed in mantle cell lymphomas, peripheral T-cell lymphomas, marginal zone B-cell lymphomas, plasma cell myelomas and Hodgkin's lymphomas. p63 was coexpressed with p53 in 18/38 p63 positive cases in which only 4 cases were strongly coexpressed. All p63+/p53+ cases were DLBCL. p63 overexpression (above 30%) cases showed significant poor survival (p=0.0228) in DLBCL. However, there was no statistically significant correlation between p63 expression and IPI score on Multivariate analysis. We could speculate that p63 could act indirectly as an oncogene by inhibiting p53 functions. Stage of differentiation of neoplastic lymphocytes appears to have a correlation with p63 expression in MLs.     

Lymphocyte immunophenotyping of B-cell lymphomas: a flow cytometric analysis of neoplastic and nonneoplastic cells in 271 cases

We have reviewed our experience with 271 B-cell lymphomas to determine the effectiveness of flow cytometry in the characterization of these malignancies. Flow cytometric immunophenotyping of the total lymphocyte and/or large lymphocyte populations confirmed the morphologic diagnosis of B-cell lymphoma in 92% of cases, which included 79% monoclonal and 13% surface immunoglobulin (SIg)-negative lymphomas. Light chain monoclonality was most frequent in low grade and follicular center cell (FCC) lymphomas, while SIg-negative cases were most common in high grade and non-FCC types. Low grade lymphomas of all histologic types had high median percentages of neoplastic cells and low T-cell percentages. Conversely, high grade lymphomas exhibited lower and less uniform median percentages of B-cells, with higher numbers of T-cells and lower CD4/CD8 ratios than low grade lymphomas. Several differences in B- and T-cells were observed between specific high grade histologic types. FCC lymphomas with a diffuse pattern had lower percentages of CD4+ cells and lower CD4/CD8 ratios than cases with a follicular pattern. Thus, immunophenotypic differences were observed between histologic types or groups with known differences in clinical course and prognosis. We conclude that flow cytometry provides reliable information on neoplastic and nonneoplastic cells in lymph nodes involved by B-cell lymphomas.     

Infiltration density of HNK 1 positive cells in non-Hodgkin's lymphomas depends on histologic subtype: an in situ morphometric analysis

Numbers and distribution of HNK-1 (Leu 7) positive cells within 115 malignant Non-Hodgkin's lymphomas (NHL) were evaluated in situ by immunomorphometry. Results on the infiltration were related to histological and clinical parameters. A mean of 4.099 +/- 350 HNK 1+ cells/microliter tumor tissue was found, which was comparable to normal (reactive) lymphatic tissues (4.441 +/- 1.235) and was about a quarter of the population density of T helper/inducer (TH) and T cytotoxic/suppressor (TS) lymphocytes together. The distribution of HNK 1+ cells within the tumors was diffuse except in nodular lymphomas of follicular center cell origin (centroblastic/centrocytic = cb/cc NHL). When evaluating the different histological subgroups, the highest number of HNK 1+ cells was found within the tumor areas of cb/cc, which contained about three times as many positive cells as the other NHL. High numbers were also found in the diffuse variant of cb/cc but not in centrocytic NHL. Different degrees of HNK 1+ cell densities were observed in lymphocytic lymphomas (4.426 +/- 754), with high numbers in about 30% of the patients. Splenic tissues of 6 hairy cell leukemias displayed lower numbers of HNK 1+ cells as compared with other low grade malignant NHL. In "large cell" NHL, the lymphoblastic subtype showed only sparse HNK 1+ cells (1.345 +/- 386). The number was significantly reduced in comparison to all other NHL (p less than 0.01) and markedly lower than in the other NHL of high malignancy (immunoblastic and centroblastic NHL, p less than 0.02). The diminuation was not due to a simple dilution phenomenon in a rapidly proliferating tumor, as TH and TS infiltrates were comparable to other NHL. Correlating results with the clinical course (available in 58 patients), significantly higher numbers of HNK 1+ cells were found in NHL of low malignancy (p less than 0.02), but patients with a favourable course did not differ from those with progressive disease (p less than 0.5). Patients treated by cytotoxic drugs showed higher numbers of HNK 1+ cells than those before or without treatment (p less than 0.02). Results on TH and TS cell numbers in comparison to HNK 1+ cells showed completely different patterns of infiltration.     

Common acute lymphoblastic leukemia-associated antigen (CALLA)-positive B cell lymphoma

We analyzed the expression of common acute lymphoblastic leukemia-associated antigen (CALLA) in 134 cases of non-Hodgkin's lymphoma of the B cell type using an immunohistochemical method. The incidence of CALLA expression in B cell lymphomas was higher in follicular lymphomas (29%) than in diffuse lymphomas (15%). Malignant lymphoma (ML), follicular small cleaved cell (FSC) according to the histologic type, showed a considerably high incidence of CALLA (43%), whereas ML, diffuse small cleaved cell (DSC) displayed a very low incidence (5%). These findings suggest the possibility that these two morphologically similar lymphomas may be derived from distinct populations of B cells [CALLA+-germinal center (GC) cells, CALLA- -germinal center (GC) cells or mantle zone (MZ) cells]. In addition, one case of DSC expressed surface immunoglobulin D (SIgD) and alkaline phosphatase (ALPase) as well as CALLA. This indicates that CALLA-positive small cleaved cell lymphoma expressing SIgD or ALPase may represent neoplastic proliferation of CALLA-positive MZ cells of secondary follicles in lymph nodes.     

Centrocytic lymphoma: a distinct clinicopathologic and immunologic entity. A multiparameter study of 18 cases at diagnosis and relapse

The clinical, pathologic, and immunologic aspects of malignant lymphoma of centrocytic type (ML,cc) were studied at diagnosis and often at relapse in 18 patients. The typical patient was a middle-aged or older man with adenopathy, often massive splenomegaly, hepatomegaly, marrow involvement, and, not infrequently, peripheral blood involvement. Histopathologically, ML,cc had a diffuse or vaguely nodular growth pattern with, predominantly, cells resembling centrocytes (cleaved follicular center cells) sometimes with admixed small round lymphocytes but with virtually no transformed cells. In 2 cases the neoplastic cells formed a mantle zone around reactive-appearing follicles. Cell suspensions and frozen sections revealed the monoclonal B-cell nature of all but 1 nonmarking case, and the polyclonality of the follicles in the 1 mantle zone case tested. The B cells had some, but not all, characteristics of both normal mantle and follicular center cells when eight nodes were studied with the use of a panel of monoclonal antibodies, peanut lectin, and endogenous alkaline phosphatase activity. Of 13 patients who underwent repeat biopsies, 1 developed a high grade unclassifiable B-cell lymphoma, and 6 had less marked changes. None of 7 patients tested had a change in light chain class. In conclusion, ML,cc is a distinct entity separable from other B-cell lymphomas in which either centrocytes or small round lymphocytes predominate.     

Common Acute Lymphoblastic Leukemia-associated Antigen (CALLA)-positive B cell lymphoma

We analyzed the expression of common acute lymphoblastic leukemia associated antigen (CALLA) in 134 cases of non Hodgkin's lymphoma of the B cell type using an immunohistochemical method. The incidence of CALLA expression in B cell lymphomas was higher in follicular lymphomas (29%) than in diffuse lymphomas (15%). Malignant lymphoma (ML), follicular small cleaved cell (FSC) according to the histologic type, showed a considerably high incidence of CALLA (43%), whereas ML, diffuse small cleaved cell (DSC) displayed a very low incidence (5%). These findings suggest the possibility that these two morphologically similar lymphomas may be derived from distinct populations of B cells [CALLA⁺-germinal center (GC) cells, CALLA⁻-germinal center (GC) cells or mantle zone (MZ) cells]. In addition, one case of DSC expressed surface immunoglobulin D (SlgD) and alkaline phosphatase (ALPase) as well as CALLA. This indicates that CALLA-positive small cleaved cell lymphoma expressing SlgD or ALPase may represent neoplastic proliferation of CALLA positive MZ cells of secondary follicles in lymph nodes. Acta Pathol. Jpn. 39: 503∼508, 1989.     

Natural killer (Leu 7+) cells in reactive lymphoid tissues and malignant lymphomas

Leu 7 (HNK-1) is a monoclonal antibody reported to identify human natural killer/killer cells. The frequency and distribution of Leu 7+ cells in 14 reactive lymphoid tissues and 47 malignant lymphomas were studied using the frozen section immunoperoxidase technic. In reactive lymphoid tissues, Leu 7+ cells were concentrated in the pale zone of germinal centers and usually were relatively scarce in the interfollicular areas. Of the malignant lymphomas, follicular lymphomas most consistently had numerous admixed Leu 7+ cells and lymphoblastic lymphomas the least. The authors' findings suggest that Leu 7+ cell accumulation in normal and neoplastic lymphoid tissue is associated at least in part with something shared by the pale zone of the normal germinal centers and the presence of neoplastic germinal centers. This association does not appear to be a simple response to lymphoid proliferation.     

Distribution of T-cell subsets in follicular and diffuse lymphomas of B-cell type.

The authors examined the number and distribution of cells reacting with monoclonal antibodies to T-cell subsets in frozen tissue sections of B-cell lymphomas (30 follicular and 17 diffuse lymphomas). In five diffuse lymphomas (two lymphocytic, three small cleaved cell) the neoplastic B-lymphocytes reacted with the monoclonal antibody anti-T1. In all other cases, the monoclonal antibodies to T-cell subsets reacted only with small lymphocytes concentrated between the follicles of follicular lymphomas and distributed randomly in diffuse lymphomas. The distribution of T cells and the T4+/T8+ ratio in follicular small cleaved and mixed lymphomas was similar, although not identical, to that seen in hyperplastic lymphoid follicles. Fewer T cells and a decrease in the T4+/T8+ ratio were seen in follicular large cell lymphoma and in diffuse large cell lymphomas. The number and distribution of T cells in follicular lymphomas is consistent with the hypothesis that there is a functional interaction between neoplastic B cells and benign T cells. No tumors were found in which the neoplastic B cells reacted with anti-T3, anti-T4, or anti-T8.     

Reactivity of Leu 1 and T101 monoclonal antibodies with B cell lymphomas (correlations with other immunological markers)

The reactivity of Leu 1/T101 monoclonal antibodies (MoAb) was studied in a series of 69 lymphomas with B cell differentiation and was correlated with other cell markers. A three step immunoperoxidase technique on frozen sections was used to test a panel of 20 MoAb: anti-human Ig (heavy and light chains), To 15 (Pan B cells), Leu 1, T101, Leu 4, Leu 3a, Leu 5, OKT 8, OKT 6, Leu 7, anti-CALLA (IOT 5), Leu 10, anti-HLA-DR, OKM 1 and anti-dendritic reticulum cells (R 4/23). T101/Leu 1 antigen was detected in 24 cases: CLL (11 of 11), diffuse centrocytic lymphomas (four of 11), follicular lymphomas (none of 12), follicular and diffuse lymphomas (seven of 10) and one unclassified low grade lymphoma. This antigen was observed in only one high grade malignant lymphoma. In follicular lymphomas, two results deserve attention: (1) T101+ lymphomas showed most frequently IgM+, IgD+ surface Ig. Inversely, T101 unreactive lymphomas displayed IgM+, IgD+ phenotype. (2) Tp67 antigen (T101, Leu 1) and CALLA (GP 100) were found to be mutually exclusive in these lymphomas. These results suggest that follicular lymphomas could be derived from two distinct germinal center cell populations: IgM+ Ig'D-, Calla+, Leu 1-/T101- and IgM+, IgD+, CALLA-, Leu+/T101+.     

Study of vimentin expression in non-Hodgkin's lymphoma using paraffin sections.

Human non-Hodgkin's lymphomas were studied by means of an avidin-biotin complex immunoperoxidase method using several monoclonal antibodies against the intermediate filament protein, vimentin. The study cases were 61 B-cell lymphomas (including 2 plasmacytomas) and 30 T-cell lymphomas (including 8 cases of mycosis fungoides). Twelve of the 61 B-cell lymphomas were positive for vimentin, and were composed of extrafollicular-center cells such as immunoblastic and plasmacytoid cells. On the other hand, lymphomas of follicular center cell origin were negative for vimentin. All cases of T-cell lymphoma except for 14 (all of 9 AILD-type lymphomas, all of 4 lymphoblastic lymphomas and one diffuse mixed small/large lymphoma) were positive for vimentin. Although vimentin expression appeared to be influenced by various conditions such as the proportion of T- and B-cell subsets, or B-cell proliferation rate, follicular center cells were constantly negative for vimentin.     

Natural killer cell subsets and natural killer-like T-cell populations in benign and neoplastic B-cell proliferations vary based on clinicopathologic features

Microenvironmental factors play a critical role in B-cell lymphomas. Most studies emphasize the role of lymphoma-infiltrating T-cells and macrophages, with few studies on natural killer cells. Natural killer cells include a less mature (CD56(bright)/CD16-) subset that is more common in lymph nodes and a more mature (CD56(dim)/CD16+) subset that is more numerous in peripheral blood. Therefore, the proportions of natural killer cells, natural killer subsets, and natural killer-like T-cells (CD3+, CD56+, and/or CD16/57+) were determined by flow cytometry in 150 cases of tissue-based B-cell non-Hodgkin lymphoma and 89 nonneoplastic tissue biopsies. Results were correlated with the clinicopathologic findings. A higher percentage of natural killer cells was found in nonneoplastic spleen versus other nonneoplastic tissue (P < .001), in splenic-based B-cell non-Hodgkin lymphoma versus other B-cell non-Hodgkin lymphoma (P < .01), and in stage II to IV diffuse large B-cell lymphoma versus stage I diffuse large B-cell lymphoma (n = 19, P = .02). The more mature natural killer subset was increased in benign spleen (P < .001) and nonsplenic B-cell non-Hodgkin lymphoma (P < .01) versus nonsplenic, nonneoplastic tissue; in diffuse large B-cell lymphoma versus other B-cell non-Hodgkin lymphoma (P < .001); and in follicular lymphoma with an intermediate follicular lymphoma international prognostic index score (n = 17, P = .04). A higher proportion of natural killer-like T-cells was seen in diffuse large B-cell lymphoma versus other B-cell non-Hodgkin lymphoma (P = .001), whereas chronic lymphocytic leukemia/small lymphocytic lymphoma contained fewer natural killer-like T-cells (P < .001). The proportions of natural killer cells, natural killer subsets, and natural killer-like T-cells vary with tissue site, type of B-cell non-Hodgkin lymphoma, and clinical stage in diffuse large B-cell lymphoma and follicular lymphoma. A higher proportion of CD56(dim)/CD16/57+ natural killer cells is found in spleen, in more aggressive B-cell non-Hodgkin lymphoma, and in follicular lymphoma with an intermediate follicular lymphoma international prognostic index score. This may be of importance with increasing therapeutic use of immunomodulatory agents.     

Frequency of CD43 expression in non-Hodgkin lymphoma. A survey of 742 cases and further characterization of rare CD43+ follicular lymphomas

CD43 expression on B cells is an immunophenotypic feature suggestive of malignancy. In the light of its diagnostic importance, we performed a comprehensive survey of CD43 expression in various types of non-Hodgkin lymphoma (NHL) and determined the frequency of its expression in routinely fixed paraffin-embedded tissues. Tissue sections in 742 cases of NHL, pretreated by the heat-induced epitope retrieval technique, were immunostained using an anti-CD43 antibody. Three categories of CD43 positivity were found: (1) more than 90% of T-cell lymphoma, mantle cell lymphoma, B-cell small lymphocytic lymphoma, and Burkitt lymphoma cases were positive; (2) 20% to 40% of nodal and extranodal marginal zone lymphoma (MZL), diffuse large B-cell lymphoma, Burkitt-like B-cell lymphoma, and lymphoplasmacytoid lymphoma cases were positive; and (3) 0% to 6% of primary splenic MZL and various types of follicular lymphoma cases were positive. Most CD43+ follicular lymphomas were predominantly large cell type with focally diffuse areas; their follicular center cell origin in 4 of 8 cases was supported by the presence of CD10 immunoreactivity and/or t(14;18) fusion gene product. CD43 is frequently detectable in a subset of B-NHL, and, thus, it seems to be a highly sensitive marker for these tumors. CD43 also may be a useful marker for classifying B-cell NHLs by virtue of its differential expression in these tumors.     

Dendritic reticulum cells and immunophenotype in aspiration biopsies of lymph nodes. Value in the subclassification of non-Hodgkin's lymphomas

Twenty-seven lymph node aspirates were identified for which histologic confirmation of non-Hodgkin's lymphoma was subsequently obtained. Fifteen aspirates interpreted as reactive hyperplasia were also examined. All aspirates were studied by immunoperoxidase on cytospin preparations with the use of antibodies DRC1, kappa, lambda, CD3, CD5, and CD20. The follicular lymphomas could not be identified reliably by morphologic examination of aspirate smears. Clusters of DRC1-positive (DRC1+) cells were present in seven of seven follicular lymphomas, one of one mantle zone lymphoma, and one of seven small lymphocytic lymphomas. Rare DRC1+ cells were present in one of one diffuse mixed and one of seven large cell lymphomas. One lymphoblastic, one Burkitt's, and two diffuse small cleaved cell lymphomas had no DRC1+ cells. None of the seven follicular lymphomas was CD5 positive (CD5+), whereas five of the seven small lymphocytic lymphomas were CD5+. Conversely, all seven follicular lymphomas were CD20-positive (CD20+), but only one of seven small lymphocytic lymphomas was CD20+. Nineteen of the lymphomas, including all 7 of the follicular lymphomas, were either kappa or lambda positive. The other eight lymphomas were T-cell (1), B-cell (1), true histiocytic (1), or "null" cell (5). The reactive aspirates had both kappa- and lambda-positive B-cells. Seven of the 15 had clusters of DRC1+ cells. To further evaluate these antibodies, the authors studied 29 additional, surgically biopsied, non-Hodgkin's lymphomas that had not been aspirated. Similar results were obtained, except that three of five diffuse small cleaved cell lymphomas had DRC1+ cells. DRC1, in conjunction with antibodies to CD5, CD20, kappa, and lambda, helps to distinguish follicular lymphoma from small lymphocytic lymphoma. DRC1 is not useful in separating reactive hyperplasia from follicular lymphoma.     

B-cell lymphomas with MYC/8q24 rearrangements and IGH@BCL2/t(14;18)(q32;q21): an aggressive disease with heterogeneous histology, germinal center B-cell immunophenotype and poor outcome

B-cell lymphomas with MYC/8q24 rearrangement and IGH@BCL2/t(14;18)(q32;q21), also known as double-hit or MYC/BCL2 B-cell lymphomas, are uncommon neoplasms. We report our experience with 60 cases: 52 MYC/BCL2 B-cell lymphomas and 8 tumors with extra MYC signals plus IGH@BCL2 or MYC rearrangement plus extra BCL2 signals/copies. There were 38 men and 22 women with a median age of 55 years. In all, 10 patients had antecedent/concurrent follicular lymphoma. Using the 2008 World Health Organization classification, there were 33 B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma (henceforth referred to as unclassifiable, aggressive B-cell lymphoma), 23 diffuse large B-cell lymphoma, 1 follicular lymphoma grade 3B, 1 follicular lymphoma plus diffuse large B-cell lymphoma, 1 B-lymphoblastic lymphoma, and 1 composite diffuse large B-cell lymphoma with B-lymphoblastic lymphoma. Using older classification systems, the 33 unclassifiable, aggressive B-cell lymphomas most closely resembled Burkitt-like lymphoma (n=24) or atypical Burkitt lymphoma with BCL2 expression (n=9). Of 48 cases assessed, 47 (98%) had a germinal center B-cell immunophenotype. Patients were treated with standard (n=23) or more aggressive chemotherapy regimens (n=34). Adequate follow-up was available for 57 patients: 26 died and 31 were alive. For the 52 patients with MYC/BCL2 lymphoma, the median overall survival was 18.6 months. Patients with antecedent/concurrent follicular lymphoma had median overall survival of 7.8 months. Elevated serum lactate dehydrogenase level, ≥2 extranodal sites, bone marrow or central nervous system involvement, and International Prognostic Index >2 were associated with worse overall survival (P<0.05). Morphological features did not correlate with prognosis. Patients with neoplasms characterized by extra MYC signals plus IGH@BCL2 (n=6) or MYC rearrangement with extra BCL2 signals (n=2) had overall survival ranging from 1.7 to 49 months, similar to patients with MYC/BCL2 lymphomas. We conclude that MYC/BCL2 lymphomas are clinically aggressive, irrespective of their morphological appearance, with a germinal center B-cell immunophenotype. Tumors with extra MYC signals plus IGH@BCL2 or MYC rearrangement plus extra BCL2 signals, respectively, appear to behave as poorly as MYC/BCL2 lymphomas, possibly expanding the disease spectrum.     

The Leukocyte Semaphorin CD100 Is Expressed in Most T-Cell, but Few B-Cell, Non-Hodgkin’s Lymphomas

The 150-kd transmembrane protein CD100 is the first semaphorin protein shown to be expressed in lymphoid tissue. CD100 is present in the interfollicular T cell zones and is also expressed by B cells in the germinal centers of secondary lymphoid follicles, but not in the mantle zones. The CD100 molecule was recently cloned, and CD100 transfectants were shown to induce homotypic aggregation of human B cells and improve their viability in vitro, suggesting that CD100 may play a role in lymphocyte aggregation and germinal center formation. We studied the expression of CD100 in 138 clinical cases representing a range of lymphoproliferative disorders, to determine whether this molecule is expressed in these neoplastic processes. In general, we found CD100 expression to be common in peripheral T-cell non-Hodgkin’s lymphomas but rare in B-cell non-Hodgkin’s lymphomas. CD100 expression was not detectable in low-grade B-cell non-Hodgkin’s lymphomas, including cases of small lymphocytic lymphoma (18 cases), marginal zone lymphoma (10 cases), and mantle cell lymphoma (10 cases), as might be expected for these neoplasms that are not of follicular center cell origin. Surprisingly, we found that the vast majority of follicular lymphomas (37 of 40 cases) as well as diffuse large-cell lymphomas of B-cell type (35 cases) did not express CD100. The neoplastic cells in 3 of 11 cases of predominantly large-cell-type follicular lymphoma did express CD100. In contrast, all five cases of high-grade, small non-cleaved (Burkitt-like) B-cell lymphoma were immunoreactive for CD100 expression, as were 18 of 20 cases (90%) of malignant T cell neoplasms. Northern blot analysis of CD100 expression correlated with immunohistochemical findings. Absence of expression of CD100 by neoplastic follicular center B cells is a common feature in follicular lymphomas, but expression of CD100 by T cells is maintained in T-cell lymphoproliferative disorders.     

Thyroid carcinoma-associated genetic mutations also occur in thyroid lymphomas

Molecular testing for mutations activating the mitogen-associated protein kinase signaling pathway is being used to help diagnose thyroid carcinomas. However, the prevalence of these mutations in thyroid lymphomas has not been reported. Therefore, we studied the prevalence of BRAF, NRAS, HRAS, and KRAS mutations in 33 thyroid lymphomas and correlated the mutational status with the clinical, pathological, cytogenetic, and immunophenotypic findings. Eleven cases were also tested for PAX8/PPARγ translocations. The lymphomas included 25 diffuse large B-cell lymphomas, 6 extranodal marginal-zone lymphomas of mucosa-associated lymphoid tissue type, and 2 follicular lymphomas. Seventeen diffuse large B-cell lymphomas were germinal center type, six non-germinal center type, and two unclassifiable (Hans algorithm). None of the cases had an associated thyroid carcinoma. Mutations of the BRAF gene were identified in six (24%) diffuse large B-cell lymphomas (D594G in three germinal center diffuse large B-cell lymphomas, K601N in two germinal center diffuse large B-cell lymphomas, and V600E in one non-germinal center diffuse large B-cell lymphoma) and of the NRAS gene in two (8%) non-germinal center diffuse large B-cell lymphomas (Q61K and Q61H). BRAF and NRAS mutations were not found in any extranodal marginal-zone lymphomas of mucosa-associated lymphoid tissue type or follicular lymphomas. HRAS and KRAS mutations were not identified in any of the cases, nor were PAX8/PPARγ translocations found. Thus, interpretation of finding a BRAF or NRAS mutation in the thyroid, particularly in preoperative thyroid aspirates, must take into account the differential diagnosis of a lymphoma. In addition to the diagnostic importance, our data also demonstrate that alteration in the mitogen-associated protein kinase pathway may have a role in the pathogenesis of some large B-cell lymphomas of the thyroid with potential therapeutic implications.     

Clonal heterogeneity assessed by flow cytometry in B-cell lymphomas arising from germinal centers

Patients with mature follicular B-cell lymphomas develop aggressive non-Hodgkin lymphomas (NHLs) during disease progression. It is controversial whether most diffuse large B-cell lymphomas (DLBCLs) and Burkitt lymphomas (BLs) emerge as de novo lymphomas or from an original follicular lymphoma. To distinguish clonally related populations in aggressive NHL, we studied the immunophenotypic features of 18 consecutive samples from 16 patients. Three flow cytometric patterns were distinguished: (1) a homogeneous neoplastic population of large B cells with phenotypic features of follicular center cells; (2) 2 atypical populations of B cells, small monoclonal B cells, and large B cells with loss of some surface antigens; and (3) 2 clonal populations of small and large B cells sharing the same light-chain isotype. The 3 flow cytometric patterns were observed, respectively, in de novo DLBCL and BL, transformation into BL, and transformation into DLBCL. Flow cytometric data can provide valuable information about the natural history of NHL.