CD5+ follicular lymphoma: a clinicopathologic study of three cases

Follicular lymphoma (FL) is a low-grade lymphoma that typically lacks CD5 antigen expression. We report 3 cases of FL with unusual expression of CD5. All cases showed histologic features of FL, including effaced nodal architecture, follicular growth pattern, and a spectrum of grades from 1 to 3 using World Health Organization criteria. In flow cytometric studies, all 3 cases showed a light chain-restricted, CD19+, CD20+ B-cell population coexpressing CD10 and low-level CD5. Immunohistochemical studies demonstrated an identical B-cell immunophenotype with weak expression of CD5 and coexpression of bcl-2 protein and the germinal center-associated markers, CD10 and bcl-6 protein. None of the cases showed expression of CD43, cyclin D1, or IgD. By molecular analysis, immunoglobulin heavy chain gene rearrangements were demonstrated in all 3 cases, and 2 of 3 cases had a t(14;18). These cases highlight the difficulty classifying these lymphomas by flow cytometric studies alone and emphasize the importance of recognizing FL in the differential diagnosis of CD5+ B-cell lymphomas.     

Precursor B lymphoblastic leukemia with surface light chain immunoglobulin restriction: a report of 15 patients

We describe 15 patients (9 children) with precursor B-cell (pB) acute lymphoblastic leukemia (ALL) with surface immunoglobulin (sIg) light chain restriction revealed by flow cytometric immunophenotyping (FCI). The same sIg+ immunophenotype was present at diagnosis and in 3 relapses in 1 patient. In 15 patients, blasts were CD19+ CD10+ (bright coexpression) in 14, CD34+ in 12, surface kappa+ in 12, surface lambda+ in 3; in 8 of 8, terminal deoxyribonucleotidyl transferase (TdT)+; and in 4, surface IgD+ in 2 and surface IgM+ in 1. The 3 CD34- cases included 1 TdT+ case, 1 with t(1;19)(q23;p13), and 1 infant with 70% marrow blasts. One adult had CD10- CD19+ CD20- CD22+ CD34+ TdT+ sIg+ blasts with t(2;11)(p21;q23). Blasts were L1 or L2 in all cases (French-American-British classification). Karyotypic analysis in 12 of 12 analyzable cases was negative for 8q24 (myc) translocation. Karyotypic abnormalities, confirmed by fluorescence in situ hybridization in 6 cases, included hyperdiploidy, t(1;19)(q23;p13), t(12;21)(p13;q22), t(9;22)(q34;q11), t(2;11)(p21;q23), and trisomy 12. The sIg light chain restriction in pB ALL might be present in neoplasms arising from the early, intermediate, and late stages of precursor B-cell maturation; sIg light chain restriction revealed by FCI does not necessarily indicate a mature B-cell phenotype, further emphasizing the importance of a multidisciplinary approach to diagnosing B-lymphoid neoplasms.     

Surface and cytoplasmic immunoglobulin expression in B-cell chronic lymphocytic leukemia (CLL)

Flow cytometric analysis of abnormal lymphocyte populations in chronic lymphocytic leukemia (CLL) has been widely reported to show weak expression of surface immunoglobulin (sIg). The international scoring system to help discriminate between CLL and other B-cell lymphoproliferative disorders lists this as the first of 5 criteria worth 1 point each. In the present study, 30 cases of CLL were studied for surface and cytoplasmic Ig expression. 23 of these 30 (76.7%) cases were positive for sIg. Of these 23, 14 cases (60.9%) showed moderate to bright sIg expression. All of these 23 cases were positive for CD5 and CD23; all were negative for CD10 and only 6 (26.1%) were positive for FMC7. 27 of 30 (90.0%) cases expressed cytoplasmic immunoglobulin (cIg) compared to 5% reported by others. This shows that cytoplasmic Ig occurs in a much greater percentage of cases than reported previously. 23 of 30 (76.7%) cases showed positivity for both surface and cytoplasmic Ig, with 15 showing kappa light chain restriction and 8 showing lambda light chain restriction. Six expressed cytoplasmic Ig only, with 4 showing kappa light chain restriction and 2 showing lambda light chain restriction. One case expressed neither cytoplasmic nor surface Ig. CD38 positivity portends a worse prognosis. Of the 29 cases tested for CD38, 13 (44.8%) were positive. Of these 13 cases, 12 were in the surface Ig/cytoplasmic Ig+ group and 1 in the cytoplasmic Ig+ group only. Also, of the 23 cases tested for CD22 expression, 16 (69.6%) were positive. These data question the use of both "weak" surface Ig expression and lack of CD22 expression as valid scoring criteria for CLL.     

Blastoid and common variants of mantle cell lymphoma exhibit distinct immunophenotypic and interphase FISH features

AIMS: The recognition of blastoid variant (BV) of mantle cell lymphoma (MCL) is based on morphological criteria. Our aim was to analyse 18 MCL cases including four BV-MCL for their clinicopathological features, proliferation index, cyclin D1 and CDK4 expression and interphase fluorescence in-situ hybridization (FISH) pattern. METHODS AND RESULTS: BV-MCL versus common MCL was characterized by a shorter overall duration of response after first-line therapy (11 months versus 28 months) and shorter overall survival (20 months versus 42 months). Interphase FISH showed a t(11;14) fusion pattern in all MCL tested cases. However, the four blastoid cases were characterized by extra copies of CCND1 signals. Using additional probes of chromosomes 11, 18, 21, these signals were shown to be the result of hypotetraploidy and not of a specific amplification of the normal or the translocated CCND1 allele. Moreover, the BV-MCL cases were characterized by a combined high percentage of cells expressing cyclin D1 and/or CDK4 with a proliferation (MIB-1-Ki67) index above 50%. Such features allowed the recognition of areas of large cell transformation in the case of secondary BV-MCL. CONCLUSIONS: Since distinction between BV and common MCL is of clinical relevance, our data underline the need to add phenotypic and cytogenetic criteria to cytomorphology for a better recognition of BV-MCL.     

Lymphomatous polyposis of the gastrointestinal tract, including mantle cell lymphoma, follicular lymphoma and mucosa-associated lymphoid tissue lymphoma

AIMS: Lymphomatous polyposis (LP) is considered to represent mantle cell lymphoma (MCL) of the gastrointestinal (GI) tract. However, a few reports have suggested that some are follicular lymphoma (FL) or mucosa-associated lymphoid tissue (MALT) lymphomas. In this study, we analysed 35 patients and clarified the clinicopathological features of LP. METHODS AND RESULTS: Paraffin-embedded tissue samples were stained immunohistochemically and analysed by tissue-fluorescence in situ hybridization (T-FISH) for IGH/CCND1 (cyclin D1) and IGH/BCL2. The average age of the patients was 58.3 years. Over half of the cases showed gastric, duodenal, small intestinal, ileocaecal and sigmoid colonic lesions (15, 19, 15, 16 and 16 cases, respectively). Phenotypically, cases were classified into three types of MCL (cyclin D1+ CD5+ CD10-) (n=12), FL (cyclin D1- CD5- CD10+) (n=14) and MALT (cyclin D1- CD5- CD10-) (n=9). T-FISH identified 11 of the 11 examined cases with MCLs to have IGH/CCND1, while seven of 10 cases with FL had IGH/BCL2, and none of the MALT cases were positive for IGH/CCND1 or IGH/BCL2. At the study endpoint, five of 12 patients with MCL were dead, two of 14 with FL and one of nine with MALT were dead of other disease. Event-free survival analysis showed significantly poorest outcome in MCL, followed by FL, while MALT was associated with a favourable outcome (P=0.0040). CONCLUSIONS: Our study emphasizes the importance of differentiating MCL, FL and MALT of LP in evaluating prognosis and hence the most suitable therapeutic regimen.     

D cyclins in CD5+ B-cell lymphoproliferative disorders: cyclin D1 and cyclin D2 identify diagnostic groups and cyclin D1 correlates with ZAP-70 expression in chronic lymphocytic leukemia

We analyzed protein expression of cyclin D1, cyclin D2, and cyclin D3 using high-resolution enzymatic amplification staining and flow cytometry in the neoplastic cells from 80 patients with CD5+ B-cell lymphoproliferative disorders. The D cyclins were expressed differentially in chronic lymphocytic leukemia (CLL), prolymphocytic leukemia (PLL), and mantle cell lymphoma (MCL) with strong staining of cyclin D1 and D2 in MCL, strong staining of cyclin D1 but weak staining of cyclin D2 in 4 of 5 PLLs, and low-level staining for both cyclins in most CLLs. No correlation between cyclin D1 and D2 and growth rates or CD38 expression was observed. However, cyclin D1 levels were significantly higher in ZAP-70+ CLL cases, although no association between ZAP-70 and cyclin D2 was detected. The results indicate that flow cytometric analysis of D cyclins may help in classification of CD5+ B-cell lymphoproliferative disorders.     

Multiple lymphomatous polyposis of the gastrointestinal tract is a heterogenous group that includes mantle cell lymphoma and follicular lymphoma: analysis of somatic mutation of immunoglobulin heavy chain gene variable region.

Multiple lymphomatous polyposis (MLP) is characterized by multiple polyps involving long segments of the gastrointestinal (GI) tract. MLP is thought to represent mantle cell lymphoma (MCL) of the GI tract; however, some cases of follicular lymphoma (FL) of the GI tract are found with a multiple polypoid appearance. In the present study, to clarify the cellular origin of MLP, clonal immunoglobulin heavy chain (IgH) gene rearrangement of four cases with MLP was amplified by polymerase chain reaction (PCR) and analyzed for the presence of somatic mutation. The IgH variable (VH) region sequences of three cases (CD5+ CD10- cyclin D1+) showed a little somatic mutation compared with the closest published germline. The other case (CD10+ CD5- cyclin D1-) was highly mutated and showed intraclonal heterogeneity (ongoing somatic hypermutation). These data indicate that three of the cases with MLP are derived from pregerminal center B cells (mantle zone B cells) and one case with MLP from germinal center B cells. Our study suggests that MLP is a heterogenous group that includes MCL and FL.     

Mantle cell lymphoma with a unique pattern of CD5 expression: a case report with review of the literatures

Mantle cell lymphoma (MCL) is a unique subtype of B-cell non-Hodgkin’s lymphoma characterized by chromosomal translocation t(11;14)(q13;q32), positive CD5, and nuclear cyclin D1 overexpression with unfavorable prognosis. We report herein a case of MCL in a 73-year-old male diagnosed with diffuse large B-cell lymphoma (ileal tumor) at another hospital, who subsequently relapsed with CD5-negative MCL. At the 1st relapse, he developed neck lymph node swelling, of which biopsy showed proliferation of atypical large pleomorphic cells with CD5-negativity by both immunohistochemistry and flow cytometry. At the 2nd relapse, he again developed an ileal tumor, of which biopsy showed positivity for CD5, CD20, and cyclin D1. In MCL, CD5-negative expression has sometimes been reported as having pleomorphic and blastoid variants. The present case was also histologically the pleomorphic type, but the CD5 expression changed from negative at the onset and the 1st relapse to positive at the 2nd relapse. This is a rare and interesting case because of the different expression of CD5 at all stage. This phenomenon made the diagnosis of MCL difficult.     

Mantle cell lymphoma with EBV-positive Hodgkin and Reed–Sternberg-like cells in a patient after autologous PBSCT: Phenotypically distinct but genetically related tumors

The case of 70-year-old man with mantle cell lymphoma (MCL) carrying t(11;14) translocation that relapsed as nodal lymphoma combining MCL and classic Hodgkin lymphoma (cHL) 9 years after autologous peripheral blood stem cell transplant (auto-PBSCT) is reported. Lymph nodes contained two separate areas of MCL and cHL-like components. Hodgkin and Reed–Sternberg (HRS)-like cells were accompanied by a prominent histiocyte background. HRS-like cells were CD5⁻, CD15⁺, CD20⁻, CD30⁺, PAX5⁺, Bob.1⁻, Oct2⁻ and EBER⁺. The MCL component expressed cyclin D1 and SOX11, whereas cyclin D1 and SOX11 expressions were reduced and lost, respectively, in HRS-like cells. Polymerase chain reaction results showed a single clonal rearrangement of the IGH gene in MCL and cHL-like components. CCND1 break apart fluorescence in situ hybridization showed split signals in both MCL and HRS-like cells, suggesting that MCL and cHL-like components were clonally related. Acquisition of p53 expression and Epstein–Barr virus (EBV)-positivity was seen in HRS-like cells. The patient died of disease progression with elevated hepatobiliary enzymes. The autopsy showed both MCL and cHL-like components around the bile ducts, splenic white pulp and bone marrow. The two components were phenotypically distinct, but genetically related, suggesting that transformation of MCL to HRS-like cells during the course of MCL in association with EBV infection.     

Demonstration of distinct antigenic profiles of small B-cell lymphomas by paraffin section immunohistochemistry.

The immunoperoxidase technique was used with antibodies against B-cell-associated antigens, including CD20, CD79a, CD10, CD23, CD43, cyclin D1, bcl-2, and kappa and lambda immunoglobulin light chains on formalin-fixed and B5-fixed tissue sections of follicular, small lymphocytic, mantle cell, and marginal zone lymphomas. Results obtained with paraffin section immunohistochemistry for CD20, CD10, CD23, and kappa and lambda light chains were compared with results obtained with flow cytometry or frozen section immunohistochemistry. Cells in all of the lymphoma types were positive for CD20 and CD79a. The antigenic profiles of the B-cell lymphomas demonstrated in paraffin sections were lymphoma type distinctive. Intrafollicular lymphocytes in follicular lymphomas were positive for CD10 and bcl-2. Small lymphocytic lymphomas expressed CD43 and CD23 and were negative for CD10 and cyclin D1. Mantle cell lymphomas characteristically expressed CD43 and cyclin D1 and were negative for CD23 and CD10. Marginal zone lymphomas were negative for CD23, CD10, and cyclin D1. All of the antibodies performed better in B5-fixed tissues, but formalin-fixed tissue immunophenotypes were always similar to those obtained on the B5-fixed tissue. These results were possible using well-fixed tissue, various antigen retrieval strategies, paraffin section reactive primary antibodies, and sensitive detection systems. Paraffin section immunohistochemistry on sections of routinely fixed tissue can be used similarly to flow cytometry and frozen section immunohistochemistry when classifying the lymphomas of small B lymphocytes.     

Large cell variants of CD5+, CD23- B-cell lymphoma/leukemia

CONTEXT: Mantle cell lymphoma (MCL), and its leukemic phase, constitute a well-studied hematologic malignancy with known overall survival, prognostic indicators, morphologic findings at diagnosis and in bone marrow, and known incidence of the bcl-1 immunoglobulin gene rearrangement. Large cell variants of B-cell lymphoma/leukemia with a mantle cell immunophenotype (CD5+, CD23-), including but not limited to blastic MCL, prolymphocytoid MCL, blastic mantle cell leukemia, and prolymphocytic mantle cell leukemia, are not as well characterized. Although blastic MCL is known to be associated with a shorter overall survival than conventional MCL, the large cell variants of B-cell lymphoma/leukemia with a mantle cell immunophenotype have not been described as fully as conventional MCL. OBJECTIVE: The purpose of the present study was to describe the large cell variants of B-cell lymphoma/leukemia with a mantle cell immunophenotype. DESIGN: Nineteen cases of large cell variants of CD5+, CD23- B-cell lymphoma/leukemia are reviewed and described in regard to morphology, bone marrow morphological findings, Cyclin D1 immunostaining, and bcl-1 analysis. Clinical data were not available owing to the varied clinical sources of the specimens. SETTING: Tertiary-care academic institution. RESULTS: Lymph node involvement in blastic CD5+, CD23- B-cell lymphoma was diffuse (100%) with a nodular component (33%) or focal mantle zone pattern (10%). Bone marrow involvement in blastic CD5+, CD23- B-cell lymphoma was seen in only 27% of cases and was composed predominantly of small, slightly irregular lymphocytes. Cyclin D1 was demonstrated in 60% of the 15 cases analyzed and more sensitive in B5-fixed tissue. Bcl-1 (performed in 5 cases) was not detected in the 4 cases of blastic CD5+, CD23- B-cell lymphoma analyzed and was detected in the case of the prolymphocytoid MCL. Cyclin D1 was demonstrated in all 4 bcl-1 negative cases and was negative in the bcl-1 positive prolymphocytoid MCL. CONCLUSION: Careful analysis of clinical data, morphology, immunophenotype, Cyclin D1 expression, and molecular analysis are required to differentiate the unusual large cell variants of MCL from other processes.     

Sub-classification of diffuse large B-cell lymphoma by semi-quantification of the CD5 expression with flow cytometric analysis

CD5+ diffuse large B-cell lymphoma(CD5+DLBCL) is known to have different characteristics than CD5-DLBCL and mantle cell lymphoma(MCL). 9 patients with CD5+DLBCL were reviewed, and the results were compared with those of 8 CD5-DLBCL and 3 cyclin D1+MCL patients. CD5+DLBCL was more closely related to many aggressive clinical features or parameters than CD5-DLBCL: 67% of the patients were older than 60 years, 67% with performance status > or = 2, 89% with serum lactate dehydrogenase level higher than normal, 78% with stage III/IV disease at diagnosis, and 78% with more than one extranodal lesion. The overall International Prognostic Index score for the patients with CD5+DLBCL was thus significantly higher than that for those with CD5-DLBCL. Immunophenotypically, CD5+DLBCL was characterized by CD5+CD10-CD19+CD20+CD21-CD23-cyclin D1-phenotype and the predominant expression of surface IgM. Of particular interest is that the survival rate of CD5+DLBCL patients was significantly inferior to that of patients with CD5-DLBCL. To further characterize CD5+DLBCL, we semi-quantified the CD5 expression in DLBCL cells. Our findings suggest that CD5+DLBCL may constitute a unique subgroup of DLBCL and, moreover, CD5+DLBCL may consist of several subgroups.     

Usefulness of CD79b expression in the diagnosis of B-cell chronic lymphoproliferative disorders

We evaluated anti-CD79b for its usefulness in the diagnosis of B-cell chronic lymphoproliferative disorders (BCLPDs), particularly chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). We analyzed 100 BCLPDs for CD5, CD19, CD20, CD23, CD79b, and surface immunoglobulin light chain (sIg) expression by 4-color flow cytometry. CD20, CD79b, and sIg expression were quantified. Correlational analysis and univariable and multivariable logistic regression models were used to determine the best combination of antigens for the immunophenotypic classification of CLL vs other BCLPDs. Positive and statistically significant Spearman pairwise correlations between CD20, CD79b, and sIg fluorescence intensity were demonstrated. In the simplest models in which a single variable was considered, cutoff points were chosen that gave misclassification rates for CLL of 16% for CD79b, 19% for sIg, and 18% for CD20. Low-intensity CD79b, CD20, and sIg are associated highly with CLL. A panel containing CD5, CD19, CD23, and sIg allowed correct classification of most cases. Addition of CD20 or CD79b improved diagnostic accuracy; CD79b was slightly better than CD20. CD79b seems to be a useful addition to a standard flow cytometry panel for the evaluation of BCLPDs.     

Mantle cell lymphoma with aberrant expression of CD10

Aims:  Morphological, immunophenotypic and genetic heterogeneity amongst mantle cell lymphomas (MCLs) can lead to difficulties in diagnosis and management. The aim was to describe the clinical and pathological features of MCLs with aberrant expression of CD10.
Methods and results:  Of 17 specimens from 13 patients, 14 expressed CD10 and three (presenting before or after a CD10+ specimen) did not. All expressed cyclin D1 and carried the t(11;14)(q13;q32)/ CCND1-IGH translocation. Similar to non-selected MCL patients, most patients had disseminated disease and an adverse clinical course. Five specimens showed pleomorphic blastoid morphology and blastoid transformation was associated with a change in phenotype, including gain or loss of CD10. Additional phenotypic variations likely to cause diagnostic difficulty were present in eight specimens: five were CD5− and five (all CD10+) expressed Bcl-6. One Bcl-6+ case carried a BCL-6 translocation and three others had extra copies of the BCL-6 gene. Sequence analysis of the immunoglobulin heavy chain variable region in five cases showed only one to have low-level somatic mutation, indicating that they did not arise from germinal centre B cells.
Conclusions:  Expression of CD10 by MCL is often associated with other variant morphological, immunophenotypic or genetic features, but does not reflect derivation from germinal centre B cells.     

CD23+ mantle cell lymphoma: a clinical pathologic entity associated with superior outcome compared with CD23- disease

Mantle cell lymphoma (MCL) commonly lacks expression of CD23. However, a significant minority of MCLs express CD23, as assessed by flow cytometric immunophenotyping (FCIP). The aims of our study were to investigate the expression of CD23 by FCIP in patients with MCL and to correlate CD23 expression with pathologic and clinical parameters, including outcome. We studied 53 patients with untreated MCL who had CD23 expression determined by FCIP. At diagnosis, 14 MCLs (26%) were CD23+ at all tissue sites, whereas 33 (62%) were CD23-, and 6 (11%) had discordant CD23 expression among different tissue sites. Patients with CD23- MCL had extranodal disease more commonly compared with patients with CD23+ MCL. Moreover, with 57-month median follow-up, the 4-year event-free and overall survival rates for CD23+ MCL were 45% and 75%, respectively, compared with 19% and 51% for CD23- MCL. In multivariate Cox regression analysis, CD23 status and leukemic-phase MCL were the most important factors predicting outcome.     

From centrocytic to mantle cell lymphoma: a clinicopathologic and molecular review of 3 decades

Mantle cell lymphoma (MCL), described almost 3 decades ago as centrocytic lymphoma and by a variety of other names, was initially recognized morphologically. MCL is a classic illustration of how the field of hematopathology and our basic understanding of neoplasia have evolved. The advent of immunophenotypic and increasingly sophisticated genotypic and cytogenetic studies, together with clinical investigations, have led to a better practical and biologic understanding of MCL and have broader implications as well. MCL is now recognized as an aggressive, difficult to treat, B-cell lymphoma with a broader morphologic spectrum than was initially appreciated and a characteristic phenotype (CD5+, CD10-, CD23-, FMC7+). Virtually all MCLs carry the translocation t(11;14)(q13;q32) with overexpression of the involved CCND1 (cyclin D1) gene. Additional cytogenetic and molecular abnormalities have been identified, including some that are early events (such as ATM gene deletion and mutation) and others that appear to be late events (such as deletions and mutations in the negative cell cycle regulatory elements p53, p16, and p18). The latter are often associated with a blastoid morphology and more aggressive clinical course. Ongoing clinical and basic investigations including microarray analysis will undoubtedly provide additional insights into MCL and perhaps more effective and specific therapeutic modalities.     

146例套细胞淋巴瘤免疫组织化学结果分析

目的：讨论套细胞淋巴瘤的免疫组织化学特征。方法：回顾性分析146例套细胞淋巴瘤的免疫组化结果,并用FISH方法检测1例Cyclin D1阴性病例是否存在t(11;14)易位。结果：套细胞淋巴瘤免疫组化阳性率为CD20：98.6%(144/146);CD79a：100%(146/146);CD5：88.4%(129/146);CyclinD1：99.3%(145/146);PAX-5：100%(122/122);CD43：84%(79/94);Ki67指数：5%~90%,中位数为20%。少部分病例异常表达CD10、Bcl6、CD23、CD56、CD3、CD45RO。FISH检测1例Cyclin D1阴性病例结果为检测到t(11;14)易位形成的IgH/CCND1融合基因。结论：套细胞淋巴瘤存在较为特征性的免疫组化表达模式,并存在异常表达现象。     

Assessment of CD10 in the diagnosis of small B-cell lymphomas: a multiparameter flow cytometric study

We evaluated the usefulness of multiparameter flow cytometry with cluster analysis in the diagnosis of a series of 100 well-characterized small B-cell lymphomas (SBCLs). The histologic diagnoses in the 100 cases were follicular lymphoma (FL) in 58, marginal zone lymphoma (MZL) in 17, small lymphocytic lymphoma in 15, and mantle cell lymphoma (MCL) in 10. Of the 58 FLs, 57 were CD10 positive (98% sensitivity). The 1 negative case was unusual in that it occurred in the small intestine. However; architectural, cytologic, and immunohistochemicalfeatures were diagnostic of FL. Of 42 other SBCLs, 2 were CD10+ (95% specificity); 1 was a CD5+/cyclin D1 + MCL, and the other was an extranodal MZL. We found that assessment of CD10 expression using multiparameter flow cytometry with cluster analysis is highly sensitive and specific for the diagnosis of FL, validating its usefulness in situations in which adequate tissue is not available for definitive histologic diagnosis.     

A unique case of mantle cell lymphoma with an aberrant CD5-/CD10+ immunophenotype and typical morphology

Mantle cell lymphoma (MCL) is a non-Hodgkin lymphoma with a poor prognosis that may be confused with less aggressive diseases, such as small lymphocytic lymphoma and follicular lymphoma. In many cases immunophenotyping, particularly analysis of reactivity for CD5 and CD10, is an important adjunct to morphology that usually distinguishes MCL from follicular lymphoma; the former is CD5(+)/CD10(-), whereas follicular lymphoma is the reverse. We report a case of MCL, initially diagnosed as follicular lymphoma, that at presentation expressed neither CD5 nor CD10. At relapse, it was still CD5(-), but CD10 was now detected. Studies for a t(11;14) translocation and CYCLIN D1 protein expression, however, permitted a revised diagnosis of MCL. An MCL with this immunophenotype and classical morphology has not been previously reported.