Histological and immunoglobulin VH gene analysis of interfollicular small lymphocytic lymphoma provides evidence for two types

Interfollicular small lymphocytic lymphoma (I-SLL) has not been well characterized and its relationship to small lymphocytic lymphoma (SLL) or chronic lymphocytic leukemia (CLL) is uncertain. Moreover, two different proliferation center growth patterns have been described with respect to reactive germinal centers. In this study, we evaluate the histological and immunophenotypic features of 13 cases of I-SLL and immunoglobulin heavy chain variable (VH) gene sequences from 10 cases. Immunophenotypic analyses indicate that cases showing either growth pattern have the same CD5-positive B cell phenotype typical of SLL or CLL. Sequence analysis revealed the use of VH, D, and J gene segments often found in CLL, although there may be more frequent use of J6. Similar to recent studies of CLL, there were approximately equal numbers of cases with either mutated or unmutated VH genes without evidence of ongoing mutation, consistent with I-SLL having either a na?ve or memory B cell origin. Interestingly, the mutational status of the I-SLL VH genes seemed to correlate with the two different histological growth patterns. These studies support the proposal that I-SLL represents SLL/CLL and suggest the recently proposed two types of CLL originating from either memory or na?ve B cells may have different histological patterns of growth in lymph nodes that show architectural preservation.     

Analysis of the immunoglobulin heavy chain gene variable region of 101 cases with peripheral B cell neoplasms and B cell chronic lymphocytic leukemia in the Japanese population

We have analyzed the immunoglobulin heavy chain (VH) gene variable regions (CDR2 and FW3) of 101 Japanese cases with peripheral B cell neoplasms. When all except one case with a deletion were graphed by frequency of replacement mutation, the 100 cases could be separated into two groups: 24 cases with zero, one and two mutations (germline or low frequency of somatic mutation); and 76 cases with three or more mutations (medium to high frequency of somatic mutation). While most mantle cell lymphoma cases (11/13) showed germline or low frequency of somatic mutation, all cases of mucosa-associated lymphoid tissue (MALT) lymphoma (11/11), follicular lymphoma (three of three cases), plasma cell myeloma (seven of seven cases) and most cases of diffuse large B cell lymphoma (DLBCL; 42/47) belonged to the latter group. These 76 cases, therefore, may be considered to show somatic hypermutation. More than half of chronic lymphocytic leukemia/small lymphocytic lymphoma cases (CLL/SLL; eight of 13) showed a hypermutated VH gene and the ratio of replacement mutation: silent mutation in CDR2 of CLL/SLL was considerably higher compared with DLBCL and MALT lymphoma, showing somatic hypermutation. When comparing VH gene type of B cell-CLL (B-CLL) among our series and those in the literature, more cases of CD5+ B-CLL in the Western literature have the VH5 and VH6 family types, while more cases in Japan are reported to have VH4 family. The occurrence of VH families in B-CLL between Japanese and Western people seems to be comparable.     

Large cell lymphoma transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma. A flow cytometric analysis of seven cases

We studied 7 cases of large cell transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) immunophenotyped by multiparameter flow cytometry. The 6 women and 1 man ranged in age from 45 to 91 years. All had previous or concurrent evidence of CLL/SLL. Morphologic features and sites of involvement of the diffuse large B-cell lymphoma (DLBCL) were heterogeneous; 2 cases had paraimmunoblastic morphologic features. Six DLBCLs had an immunophenotype consistent with CLL: CD19+, CD5+, CD23+, and FMC7 negative (3 cases) or very dim (2 cases); 1 case was not studied for FMC7. CD20 was dim in 3 of these, moderate to bright in 2, and variable in 1. Surface immunoglobulin was dim in 2 cases and moderate or bright in 4. Five of 6 expressed CD38. Comparison with the immunophenotypes of the previous or coexistent CLL/SLL (4 of 6 cases) revealed minor modulations in antigen expression but no major alterations. The seventh DLBCL lacked CD5 expression, but otherwise had immunophenotypic features similar to CLL. These findings indicate that DLBCL arising in CLL/SLL tends to retain a CLL immunophenotype, in contrast with de novo CD5+ large cell lymphomas that uncommonly express such a phenotype.     

Expression of members of the immunoglobulin VH3 gene families is not restricted at the level of individual genes in human chronic lymphocytic leukemia.

Previous studies on the repertoire of Ig VH genes utilized in the malignant cells of chronic lymphocytic leukemia (CLL) have suggested a non-random expression pattern. In particular, individual genes from the VH1, VH5, and VH6 gene families have been frequently found in CLL. With regard to other VH gene families, including the large VH3 family which is expressed in greater than 50% of CLL cases, it is unknown whether CLL cells utilize either a broad or a restricted repertoire of VH genes. In the present paper, we analyzed the VH genes expressed in a collection of 11 CLL cases. The results of these experiments demonstrate that there is no apparent restriction in the usage of individual members of the VH3 gene families in CLL.     

Analysis of the immunoglobulin heavy chain gene variable region of CD5-positive diffuse large B-cell lymphoma.

To clarify the cell origin of CD5+ diffuse large B-cell lymphoma (DLBCL), we analyzed and compared the variable region of the immunoglobulin heavy chain gene (VH gene) in eight cases of CD5+ DLBCL and 23 cases of other CD5+ B-cell neoplasms; 10 cases of chronic lymphocytic leukemia (CLL), one case of small lymphocytic lymphoma, one case of hairy cell leukemia, and 11 cases of mantle cell lymphoma. CD5+ DLBCL were comprised of two cases of de novo lymphoma of nodal origin, five cases of de novo lymphoma of extranodal origin, and one case of Richter transformation. Whereas all cases of mantle cell lymphoma except one showed a germ line or low mutation frequency of the rearranged VH gene, the rearranged VH genes in both CD5+ CLL and CD5+ DLBCL were heterogeneous. The degree of somatic mutation of CD5+ CLL and CD5+ DLBCL ranged between approximately 0 to 15.0% and 0.7 to 12.9%, respectively. High frequency of expression of the VH4 family in both CD5+ CLL and CD5+ DLBCL was found. Moreover, none of the three cases of CD5+ DLBCL examined exhibited intraclonal diversity. These findings may be common characteristics of the rearranged VH gene of CD5+ CLL and CD5+ DLBCL and suggested that the cell origin of CD5+ DLBCL was the same as that of CD5+ CLL.     

Chronic lymphocytic leukemia/small lymphocytic lymphoma associated with IgM paraprotein

We studied the clinicopathologic, immunophenotypic, and cytogenetic features of 26 patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) associated with serum IgM paraprotein. The study group (16 men; 10 women; median age, 64 years; range, 40-82 years) represents approximately 2.5% of CLL/SLL cases at our institution. The paraprotein level ranged from 1 to 14 g/L (median, 4 g/L). Neoplasms in bone marrow were composed of small round lymphocytes arranged in nodular (n = 6), diffuse (n = 5), interstitial (n = 5), or mixed (n = 10) patterns. All cases were positive for monotypic surface immunoglobulin light chain, IgM/IgD, CD5, CD19, CD20, and CD23. CD11c (14/20 [70%]), CD79b (11/19 [58%]), FMC-7 (11/26 [42%]), CD22 (8/20 [40%]), and ZAP-70 (6/19 [32%]) were expressed in subsets of cases. Of 17 bone marrow specimens assessed by conventional cytogenetics, 6 were abnormal and 11 were diploid. The overall survival of this group (median follow-up, 24 months) was not significantly different from that for an age-, sex-and stage-matched group of 52 CLL/SLL patients without IgM paraprotein (P = .60). We conclude that CLL/SLL cases with serum IgM paraprotein are similar to other CLL/SLL cases in their clinicopathologic and immunophenotypic features.     

Non-Hodgkin's lymphomas (from Rappaport to WHO 2001 and nowadays). Review

In the last decades, considerable changes in the classification of lymphomas have been made. In addition to morphology and immunohistochemistry, the last WHO (2001) classification also utilizes cytogenetics and molecular biology. In many cases classification notices oncogenic mechanisms. The authors describe some differences in immunophenotype in certain entities: chronic lymphocytic leukaemia/small lymphocytic lymphoma--CLL/SLL, follicular lymphoma--FL, mantle cell lymphoma--MCL, diffuse large B-cell lymphoma--DLBCL, and anaplastic large cell lymphoma--ALCL, mainly with respect to prognosis. The authors point out to heterogeneity within the individual types of lymphomas from the point of view of morphology, immunohistochemistry and molecular biology. Recently it has been shown, that differences in prognosis are not limited to individual nosologic entities, but also may be found within the particular category of lymphoma. For example, CLL/SLL is divided in two different subunits according to mutational status of variable segment (VH) of the immunoglobulin heavy chain gene. The cases with unmutated VH segment display progressive disease which is in contrast to cases with the same morphology but with mutated VH segment. Similar differences were found in MCL. Attention is drawn to oncogenic and apoptosis-regulating mechanisms, such as gene p53 and the Bcl-2 family.     

中国人群慢性淋巴细胞白血病免疫球蛋白重链可变区基因组成及突变分析

目的 研究中国慢性淋巴细胞白血病(chronic lymphocytic leukemia,CLL)患者免疫球蛋白重链可变区(immunoglobulin variable heavy chain region,IGVH)基因各个片段的组成以及突变情况.方法 应用多重PCR技术扩增64例CLL患者的IGVH基因片段,纯化PCR扩增产物后直接测序,应用IMGT/V-QUEST及IGBlast数据库分析,明确VH基因有无突变和突变位置,以及VH、DH,JH家族各个成员组成情况.结果 64例CLL患者中,VH3家族31例(48%)、VH4家族26例(41%)、VH1家族4例(6%)、VH2家族2例(3%)、VH7家族1例(2%).44例患者发生体细胞突变,占CLL患者的69%;20例无突变,占CLL患者的31%,其中6例(9%)VH基因的同源性为100%.VH4家族中有9例无突变(9/26,35%);VH3家族中8例无突变(8/31,26%);VH1家族中1例无突变(1/4,25%).在所检测的CLL标本中,VH4-34是最常见的VH基因片段,检测出8例(13%),其中无突变3例;其次为VH4-59,检测出7例(11%),无突变者3例.DH基因中DH3家族最常见,有25例(39%);其中11例(11/20,55%)出现在无突变组中.无突变组中最常见的DH基因片段为DH3-10和DH3-22,各为4例(4/20,20%).JH基因中JH6家族最常见,检测出23例(36%),其中9例出现在无突变组中(9/20,45%).结论 中国CLL患者IGVH基因家族表达比例和突变情况与西方国家存在显著差异,推测可能与不同的种族和环境中的抗原选择有关,其预后意义有待进一步探讨.     

Genetic characterization of the paraimmunoblastic variant of small lymphocytic lymphoma/chronic lymphocytic leukemia: A case report and review of the literature

Paraimmunoblastic variant of small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) is characterized by a diffuse proliferation of cells, called paraimmunoblasts, normally located on the pseudoproliferation centers. Patients usually present with multiple lymphadenopathies and a rapid and aggressive progression of the disease. We report a case with paraimmunoblastic variant of SLL/CLL genetically well-characterized by conventional cytogenetics, comparative genomic hybridization (CGH), IgH/BCL-1, IgH/BCL-2, and p53 fluorescent in situ hybridization (FISH) probes and polymerase chain reaction (PCR) for detection of IgH/BCL-2 translocation. A complex karyotype was found, with p53 deletion confirmed by CGH and FISH; however, no translocations involving either BCL-2 or BCL-1 and the immunoglobulin heavy chain gene were identified. A literature review shows only 20 previously reported cases, 6 of which involve genetic studies.     

Fine-needle aspiration diagnosis of squamous cell carcinoma in a lymph node involved with small lymphocytic lymphoma: case report and review of the literature

Diagnosis of two distinct malignant entities existing concurrently and at the same location (synchronous malignancy) by fine- needle aspiration (FNA) is unusual but may occur. Small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) in particular is associated with an increased incidence of secondary tumor, likely due to associated immunodeficiency. Co-occurrence of some carcinomas such as squamous cell carcinoma (SCC), may show especially aggressive behavior. A 57-year-old Caucasian male presented with recurrent upper extremity lymphedema and diffuse lymphadenopathy of the axillary and cervical regions. FNA of a large cervical lymph node was diagnostic for both atypical lymphocytic proliferation and SCC. Flow cytometric analysis showed the atypical lymphocytic proliferation to be positive for CD5, CD23, CD19, CD20, HLA-DR, CD38, and the population was kappa light chain restricted. These cells were negative for CD-10 and FMC-7 antigens, suggesting a phenotype of B-cell SLL/CLL. We report a rare occurrence of metastatic SCC to a lymph node infiltrated by SLL/CLL. The diagnosis was achieved by a combination of cytomorphologic examination of FNA smears, immunohistochemical staining of cell block material, and flow cytometry on the sample obtained by FNA. To the best of our knowledge, only three cases of SCC metastasis to SLL/CLL diagnosed by FNA have been reported in the English literature. Though rare, awareness of such a possibility and careful cytological examination under the appropriate clinical conditions is warranted.     

Fine-needle aspiration biopsy findings in patients with small lymphocytic lymphoma transformed to hodgkin lymphoma

Although small lymphocytic lymphoma (SLL) is an indolent lymphoma, approximately 5% of cases can transform to a higher-grade lymphoma, rarely Hodgkin lymphoma (HL). We report the fine-needle aspiration (FNA) results of 6 cases of SLL/chronic lymphocytic leukemia (CLL) that transformed to HL. FNA findings were correlated with the histologic features and clinical follow-up. The patients included 5 men and 1 woman, ranging in age from 49 to 72 years at the time of SLL/CLL diagnosis with time for development of HL ranging from 0 to 95 months (mean, 49.3 months). The FNA diagnoses were SLL with HL transformation (2 cases), SLL with large atypical cells (1 case), and atypical lymphoid proliferation with large atypical cells (3 cases). Flow cytometry performed in 5 cases (2 FNA specimens) demonstrated a monoclonal B-cell population with CD19/CD5 coexpression.The presence of large atypical mononucleated and binucleated cells in lymph node FNA specimens from patients with SLL/CLL with progressive adenopathy should raise the possibility of transformation to HL. In these cases, histologic confirmation is always recommended, not only to differentiate HL transformation from other entities but also for subclassification of HL.     

CD200 (OX-2 membrane glycoprotein) expression in b cell-derived neoplasms

We studied the expression of CD200, an immunoglobulin superfamily membrane glycoprotein, in a wide range of B cell-derived neoplasms by immunohistochemical staining of paraffin-embedded tissue sections. In addition to chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), CD200 is expressed in other B-cell lymphoproliferative disorders, including hairy cell leukemia. In addition, neoplastic cells in classical Hodgkin lymphoma are immunoreactive for CD200. CD200 was previously reported to be expressed in acute myeloid leukemia, and we find that it is also expressed in B-lymphoblastic leukemia/lymphoma. We conclude that CD200 may be a useful immunophenotypic marker in the evaluation of B cell-derived neoplasms. Furthermore, since an anti-CD200 immunotherapeutic agent is in clinical trials, a number of B cell-derived neoplasms in addition to CLL/SLL may be suitable therapeutic targets.     

Different gene expression in immunoglobulin-mutated and immunoglobulin-unmutated forms of chronic lymphocytic leukemia

The mutation status of the immunoglobulin heavy chain variable regions (IgVH) has been found to be a good prognostic indicator for B-cell chronic lymphocytic leukemia (CLL) because unmutated VH genes are associated with rapid disease progression and shorter survival time. To study the differences in gene expression between the Ig-unmutated and Ig-mutated CLL subtypes, we performed gene expression profiling on 31 CLL cases and investigated the VH gene mutation status by sequencing. The array data showed that the greatest variances between the unmutated (20 cases) and the mutated (11 cases) group were in expressions of ZAP70, RAF1, PAX5, TCF1, CD44, SF1, S100A12, NUP214, DAF, GLVR1, MKK6, AF4, CX3CR1, NAFTC1, and HEX. ZAP70 was significantly more expressed in the Ig-unmutated CLL group, whereas the expression of all the other genes was higher in the Ig-mutated cases. These results corroborate a recent finding, according to which the expression of ZAP70 can predict the VH mutation status and suggest that RAF1, PAX5, and other differentially expressed genes may offer good markers for differentiating unmutated cases from mutated cases and thus serve as prognostic markers.     

骨髓活检组织淋巴瘤的病理诊断和分型

目的 探讨组织形态改变、免疫组织化学、基因重排在淋巴瘤骨髓侵犯的病理诊断和分型中的作用。材料与方法 对62例甲醛固定、石蜡包埋的骨髓活检组织,分别做了组织学、EnVision法观察和免疫球蛋白重链(IgH)基因和TCRγ基因重排检测。结果 慢性淋巴细胞性白血病／小淋巴细胞淋巴瘤(CLL／SLL)的异型淋巴细胞呈小梁间结节状或散在分布,有时可见假滤泡结构。滤泡型淋巴瘤(FCL)表现为结节性小梁旁或小梁间的浸润,结节内小淋巴样细胞松散聚集。淋巴浆细胞性淋巴瘤(LPL)主要为小梁间弥散浸润,在小而圆的淋巴细胞间可见散在数量不等的浆细胞样淋巴细胞。边缘区淋巴瘤(MZL)则见模糊的或界限不清的小梁间或小梁旁结节,一些细胞胞质透明。套细胞性淋巴瘤(MCL)异型细胞小到中等大小,缺乏副免疫母细胞和假滤泡。毛细胞性淋巴瘤(HCL)瘤细胞胞膜多清晰,胞质丰富透明,常形成荷包蛋样表现。霍奇金病可见大核瘤细胞,核仁明显。T-非霍奇金淋巴瘤(NHL)浸润骨髓主要为小梁间间质性散在或弥漫分布,胞质多透明,核有芋艿样或脑回状改变,DLBL造血细胞间体积大的瘤细胞散在或弥漫分布。CD3对T细胞来源、CD20和CD79对B细胞来源淋巴瘤有鉴别诊断价值,cyclin D1和(SD5阳性对MCL具有诊断性价值,bcl-2和CD10阳性则对FCL具有诊断性意义,而CLL／SLL除了(SD20和CD79阳性外,也可CD5和CD23阳性。HCL的瘤细胞CD25强阳性。CD15、CD30和Fascin也适用于骨髓霍奇金病的诊断。骨髓中CLL／SLL,LPL,MZL及DLBL的IgH重排率(80％、60％、66．7％、70％)及T—NHL的TCRγ重排率(66．7％)较高。结论 综合组织形态改变、免疫组织化学和IgH／TCRγ重排检测,有助于淋巴瘤骨髓侵犯的诊断和分型,有助于发现骨髓中为数不多的淋巴瘤细胞。     

CD5-positive B-cell malignancies frequently express cross-reactive idiotypes associated with IgM autoantibodies.

Using monoclonal antibodies (MAb) specific for cross-reactive idiotypes (CRIs) associated with human monoclonal IgM autoantibodies, we examined 57 biopsy specimens that previously had been noted to have immunohistologic features of CD5-positive B-cell small lymphocytic (SL) non-Hodgkin's lymphoma (NHL). Twenty-five lymphoma specimens were noted to be from patients with chronic lymphocytic leukemia (CLL). Eight of thirty-four (24%) immunoglobulin (Ig) kappa light-chain expressing lymphomas reacted with 17.109, a MAb specific for a major CRI encoded by a conserved Ig kappa variable region gene (Vk gene) of the VkIIIb sub-subgroup. All 17.109-reactive tissues and two 17.109-negative specimens were recognized by another MAb specific for VkIIIb framework determinant(s). Seven of all fifty-six (13%) Ig-expressing tumors bound G6, a MAb specific for an autoantibody heavy-chain-associated CRI that is encoded by a conserved antibody heavy chain variable region gene(s) (VHgene) of the VH1 subgroup. All seven G6-positive lymphomas and two G6-negative tumors reacted with Cc1, another MAb specific for a rheumatoid factor heavy-chain-associated CRI. A third autoantibody-heavy-chain-associated CRI, termed Lc1, was expressed by seven (13%) other lymphomas. Finally, a fourth MAb specific for RF heavy-chain-associated CRI, named B6, detected two additional tumors. The expression frequencies of autoantibody-associated CRIs among SL NHL patients without peripheral lymphocytosis did not differ from those noted among patients with CLL but were significantly higher than those observed among patients with NHL of follicular center-cell origin. These data imply that the malignant B cells of patients with either CD5-positive B-cell SL NHL or CLL express a restricted set of Ig V genes that have not substantially diversified from the germline DNA.     

Small lymphocytic lymphoma with perifollicular, marginal zone, or interfollicular distribution.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) typically involves nodal or extranodal tissues as a diffuse proliferation with pseudofollicular growth centers obliterating normal architecture. We describe 16 cases of CLL/SLL in which the neoplasm was confined to the marginal zone, perifollicular, or interfollicular regions surrounding benign lymphoid follicles in either nodal or extranodal sites. Twelve of 12 (100%) patients with adequate staging data had disseminated disease (Stage III or IV) at presentation. Eight of the 16 (50%) patients had absolute peripheral lymphocytosis (range, 5 to 30 x 10(9)/L). Pseudofollicular growth centers were identified in 14 of 16 cases (87.5%). Immunophenotypic studies revealed that the tumor cells were positive for CD20 (16/16) and CD5 (11/11) in all cases examined. CD23 was positive in 12 of 14 (86%) interpretable cases. IgM and IgD were positive in 13 of 14 (93%) and 10 of 10 (100%) interpretable cases, respectively. All cases were negative for CD3 (16/16), CD45RO (16/16), CD10 (15/15), and cyclin D1 (15/15). We conclude that CLL/SLL can have unusual patterns of involvement, including marginal zone, perifollicular, and interfollicular patterns that can be difficult to recognize histologically. Thirteen of 16 (81%) cases in this study were misinterpreted by the referring pathologists. Recognition of proliferation centers coupled with demonstration of a CD5+ CD23+ B-cell immunophenotype establishes the correct diagnosis of CLL/SLL.     

B cell repertoire in adult antigen-free and conventional neonatal BALB/c mice. I. Preferential utilization of the CH-proximal VH gene family PC7183

Early in ontogeny B cells preferentially use VH gene families which are most adjacent to the genes coding for the constant part of the immunoglobulin molecule. In conventional adult mice, however, a random usage of VH gene families has been found. We investigated the role of exogenous antigenic stimulation on this normalization of VH gene usage by B cells. Therefore, we made use of adult germ-free BALB/c mice fed a chemically defined ultrafiltered antigen-free diet (GF-CD) and neonatal conventional BALB/c mice. Both the adult GF-CD and the newborn conventional mice represent situations with minimal exogenous antigenic stimulation. The results obtained with RNA dot blot hybridization with probes specific for the different VH gene families showed in hybridomas from adult GF-CD BALB/c mice a preferential usage of the CH-proximal VH gene family PC7183. In hybridomas from 5-day-old conventional BALB/c mice a less frequent usage of the J558 VH gene family was found and an increased usage of the PC7183 VH gene family than what would be expected from random usage. Evidence is presented that the RNA giving a positive signal with the PC7183 probe represents functional messages for IgM production.     

Value of CD23 determination by flow cytometry in differentiating mantle cell lymphoma from chronic lymphocytic leukemia/small lymphocytic lymphoma.

Mantle cell lymphoma (MCL) and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) share many morphologic and immunophenotypic features. In addition to histomorphologic examination, it is customary to use the absence of CD23 to differentiate MCL from CLL/SLL, based primarily on reported comparisons of immunohistochemical staining of tissue sections. These findings are widely extrapolated to flow cytometric analysis, although available data are contradictory and not sufficiently detailed. We compared expression of CD23 by flow cytometry in 22 cases of MCL and 25 cases of CLL/SLL. Lymphoma cells in 12 of 22 MCLs were negative for CD23, and 10 showed dim expression. In contrast, none of 25 CLL/SLLs were negative for CD23, 4 were dimly positive, and 21 were moderately or brightly positive. Thus, a significant proportion of MCL exhibited overlap of CD23 expression in the low-intensity range with CLL/SLL. Clinically, there was no correlation between the intensity of CD23 expression and clinical stage at diagnosis or survival. These findings emphasize that by flow cytometry, MCL can be differentiated reliably from CLL/SLL using CD23 if negative expression is observed. However, with dimly positive expression, interpretation should be cautious.     

B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma involving bone marrow with an interfollicular pattern

B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) may involve the bone marrow in nodular, interstitial, diffuse, or mixed patterns. However, B-cell CLL/SLL associated with large reactive germinal centers (the so-called interfollicular pattern) involving the bone marrow is not reported. We describe 2 examples of B-cell CLL/SLL that subtotally replaced the bone marrow with an interfollicular pattern. In both cases, the neoplasms were composed of small round lymphoid cells; proliferation centers also were present. The neoplasms surrounded large reactive germinal centers that were devoid of peripheral mantle zones. The germinal centers were paratrabecular and nonparatrabecular in case 1 and nonparatrabecular in case 2. Flow cytometry immunophenotypic studies done on bone marrow aspiration samples of both cases showed a uniform population of neoplastic cells positive for pan-B-cell antigens and the CD5 and CD23 antigens. Immunohistochemical studies done on bone marrow biopsy sections supported the flow cytometry results and demonstrated that the germinal centers were negative for BCL-2. B-cell CLL/SLL may rarely involve the bone marrow with an interfollicular pattern. Knowledge of this pattern will prevent confusion with follicle center lymphoma and large cell transformation, both of which initially were considered in the differential diagnosis of these cases.