Mantle cell lymphoma: recent insights into pathogenesis, clinical variability, and new diagnostic markers

Mantle cell lymphoma (MCL; previously called centrocytic lymphoma or lymphocytic lymphoma of intermediate differentiation) is a distinct subtype of B-cell lymphoma, accounting for approximately 3%-10% of all lymphoma diagnoses. The name refers to the growth pattern in early disease presentation resembling the normal mantle zone that surrounds the germinal center of the B-cell follicle. The hallmark of MCL is the t(11;14)(q13;q32), resulting in aberrant expression of the CCND1 gene and expression of cyclin D1 in the tumor cells. Expression and genomic profiling of MCL have provided new insight into the pathogenesis and will be summarized in this review. Pitfalls in the differential diagnosis versus B-cell chronic lymphocytic leukemia, B-cell prolymphocytic leukemia, cyclin D1-positive diffuse large B-cell lymphoma, hairy cell leukemia, and plasma cell tumors will be discussed, including the usefulness new diagnostic markers SOX11 and CD200. In situ MCL, MCL with an indolent clinical course, and cyclin D1-negative MCL are other topics of this review.     

CD5(-) diffuse large B-cell lymphoma with peculiar cyclin D1+ phenotype. Pathologic and molecular characterization of a single case

Increased expression of cyclin D1 is notoriously associated with mantle cell lymphoma because of translocation t(11;14)(q13;q32) or variants involving the cyclin D1 gene. We present an unusual case of CD5-negative diffuse large B-cell lymphoma expressing cyclin D1 in the absence of translocation by fluorescence in situ hybridization analysis. Using array-comparative genomic hybridization, we found a complex karyotype without the characteristic chromosomal aberrations accompanying cyclin D1 translocation in mantle cell lymphoma; instead, there was monoallelic deletion of AKT interacting protein and glycogen synthase kinase-3 β genes, both involved in the AKT/glycogen synthase kinase-3 β cascade-controlling nuclear levels of cyclin D1. These findings suggest that posttranslational events regulating cyclin D1 activity may take place also in a subset of diffuse large B-cell lymphomas and contribute to lymphomagenesis. As a consequence, the sole cyclin D1 positivity by immunohistochemistry may not be enough to distinguish pleomorphic/blastoid mantle cell lymphoma from diffuse large B-cell lymphoma. Search for t(11;14) with fluorescence in situ hybridization probes should always be performed in doubtful cases.     

Composite mantle cell and diffuse large B-cell lymphoma: report of two cases

Composite lymphomas are rare and involve the concurrent evolution of 2 distinct lymphoma types within a single organ or tissue. This study describes 2 cases of composite mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL), which has not previously been reported. Each case demonstrated distinct populations of CD20 positive small and large atypical B cells. In both cases, only the small lymphocytes were positive for CD5 and cyclin D1, and fluorescence in situ hybridization (FISH) showed a t(11;14) translocation in the small lymphocytes but not in the large cells. Molecular studies for B-cell clonality showed a possible clonal relationship between the 2 components in one case but not the other. This study describes in detail the morphology, immunophenotype, FISH, and molecular analysis of both components in each case. To the authors' knowledge, this represents the first report of juxtaposition of MCL with DLBCL that does not represent transformation of the mantle cell component.     

bcl-1 REARRANGEMENT AND CYCLIN D1 PROTEIN EXPRESSION IN MANTLE CELL LYMPHOMA

Centrocytic lymphoma, or mantle cell lymphoma (MCL), is characterized by a chromosomal translocation t(11;14) (q13;q32) involving the bcl-1 locus on chromosome 11. Cyclin D1 is a cell-cycle regulatory protein essential for G1–S transition and has been identified as a potential transforming gene affected by the translocation. In this study, 32 cases of MCL were analysed for the bcl-1 rearrangement and cyclin D1 protein expression. In 17 cases, a rearrangement at the major translocation cluster of bcl-1 could be detected. Twenty-four cases exhibited nuclear cyclin D1 expression that was not detectable in other B-cell lymphomas ( n =40) or in normal B-cells. In nine MCL samples, cyclin D1 was expressed without a detectable bcl-1 rearrangement. The detection of a t(11;14) by means of classical cytogenetics in one of these cases, however, may suggest that this discrepancy could be due to chromosomal breakages outside the typical translocation cluster region. In two cases, a bcl-1 rearrangement was not accompanied by cyclin D1 expression. This study provides further evidence that cyclin D1 is involved in the pathogenesis of MCL and can be exploited as a diagnostic marker in the differential diagnosis of B-cell lymphomas and in the identification of MCL.     

逆转录聚合酶链反应检测石蜡包埋组织中细胞周期蛋白D1 mRNA对套细胞淋巴瘤的诊断价值

目的 探讨用逆转录聚合酶链反应（RT-PCR）法和竞争性RT-PCR法检测套细胞淋巴瘤（MCL）石蜡包埋组织中细胞周期蛋白D1（cyclin D1）蛋白和mRNA在常规病理工作中的可行性及其诊断和鉴别诊断价值。方法 收集淋巴结内MCL38例、对照组包括结内小B细胞淋巴瘤58例（B小淋巴细胞性淋巴瘤14例,淋巴浆细胞性淋巴瘤3例,滤泡性淋巴34例,淋巴结边缘区B细胞淋巴瘤7例）和淋巴结反应性增生病例20例,用免疫组织化学EnVision法和RT-PCR法、竞争性RT-PCR法检测cyclin D1蛋白及其mRNA的表达,以看家基因PGK作为内对照检测RNA。结果 （1）38例结内MCL中,cyclin D1蛋白阳性率为71．1％（27／38）,对照组均为阴性。（2）116例标本中,可检出内对照PGK基因mRNA表达103例（88．8％）。38例MCL中PGK阳性36例（94．7％）。（3）38例结内MCL中,34例可检出cyclin D1 mRNA表达,去除PGK和cyclin D1 mRNA均阴性的2例,MCL中cyclin D1 mRNA表达的阳性率为94．4％（34／36）。对照组中B小淋巴细胞性淋巴瘤1例检出cyclin D1 mRNA表达,其余病例均未检出cyclin D1 mRNA表达。PCR结果全部经测序证实。（4）用竞争性RT-PCR,38例结内MCL中27例可检出cyclin D1 mRNA高表达,去除2例PGK也为阴性的病例,MCL中cyclin D1 mRNA高表达率为75．0％（27／36）。对照组小B细胞恶性淋巴瘤及淋巴结反应性增生无1例有cyclin D1 mRNA高表达。结论 RT-PCR方法和竞争性RT-PCR方法可在石蜡包埋组织中检测cyclin D1 mRNA的表达,均可用于MCL的诊断。     

Mantle cell lymphoma disguised as marginal zone lymphoma

We report a case of mantle cell lymphoma histologically indistinguishable from marginal zone lymphoma. An 83-year-old man presented with a 9.0-cm, slowly enlarging axillary mass. Microscopically, the neoplastic process was largely interfollicular, surrounding residual follicular centers, some of which had discernible small lymphocyte mantles. Overall, the morphologic pattern was highly suggestive of marginal zone lymphoma. However, flow cytometric and immunohistochemical results, including cyclin D1 positivity, revealed an immunophenotype that fit with mantle cell lymphoma. The differential diagnosis of mantle cell lymphoma is broad, and it is well known that mantle cell lymphoma can assume a number of histologic appearances, including, infrequently, that of more indolent B-cell non-Hodgkin lymphomas. Although not pathognomonic, cyclin D1 positivity is highly specific for mantle cell lymphoma and is key in distinguishing these clinically dissimilar malignant lymphomas. In recent years, detection of cyclin D1 has expanded the recognizable histologic spectrum of mantle cell lymphoma.     

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.     

p27(Kip1) immunostaining for the differential diagnosis of small b-cell neoplasms in trephine bone marrow biopsies.

The distinction between mantle cell lymphoma (MCL) and other small B-cell non-Hodgkin lymphomas (NHL) is important because MCL has a more aggressive clinical course. In bone marrow (BM) biopsy specimens, this distinction can be particularly difficult. Although cyclin D1 immunostaining and molecular detection of the t(11;14) translocation are highly specific markers for MCL, they fail to detect a proportion of cases. We have recently described that MCL typically lacks detectable expression of the cyclin-dependent kinase inhibitor p27(kip1) protein by immunostaining, which is expressed at high levels in most small B-cell NHL inversely correlated to the proliferation rate. We therefore examined whether p27(kip1) immunostaining could be a useful adjunct for the differential diagnosis of small B-cell NHL infiltrates in the BM. Trephine BM biopsy specimens of 96 patients, including well-characterized MCL (19 cases), B-cell chronic lymphocytic leukemia (27 cases), follicular lymphoma (18 cases), hairy cell leukemia (22 cases), and marginal zone lymphoma (10 cases) as well as 10 reactive BM, including five with benign lymphoid aggregates were investigated. In addition, the presence of a t(11;14) translocation involving the major translocation cluster was studied by PCR in all MCL. All cases of B-cell chronic lymphocytic leukemia, follicular lymphoma, and marginal zone lymphoma revealed a strong p27(kip1) nuclear staining in the majority of neoplastic cells. Fourteen (78%) cases of MCL were p27(kip1)-negative in the tumor cells, whereas four cases revealed a weak nuclear positivity. Seventeen (77%) cases of hairy cell leukemia were also either completely negative for p27(kip1) or showed a faint positive staining in a minority of the neoplastic cells. Nine of 19 cases (47%) of MCL showed a bcl1 rearrangement involving the major translocation cluster region. These findings demonstrate that p27(kip1) immunostaining is a valuable additional marker for the differential diagnosis of small B-cell NHL infiltrates in BM biopsies. The reduction or lack of p27(kip1) protein expression in MCL, as well as in hairy cell leukemia, might be an important event in the pathogenesis of these disorders.     

Immunohistochemical detection of cyclin D1 using optimized conditions is highly specific for mantle cell lymphoma and hairy cell leukemia.

Mantle cell lymphoma (MCL) is more aggressive when compared with other lymphomas composed of small, mature B lymphocytes. Cyclin D1 is overexpressed in MCL as a result of the translocation t(11;14)(q13;q32). Cyclin D1 immunohistochemistry in fixed, paraffin-embedded tissue contributes to the precise and reproducible diagnosis of MCL without the requirement of fresh tissue. However, its use in bone marrow biopsies is not well established. In addition, increased levels of cyclin D1 mRNA have been found in hairy cell leukemia but have not consistently been detected by immunohistochemistry. We used a polyclonal antibody and heat-induced antigen retrieval conditions to evaluate 73 fixed, paraffin-embedded bone marrow, spleen, and lymph node specimens with small B-cell infiltrates, obtained from 55 patients. Cyclin D1 was overexpressed in 13/13 specimens of MCL (usually strong, diffuse reactivity in most tumor cells) and in 14/14 specimens of hairy cell leukemia (usually weak, in a subpopulation of tumor cells). No reactivity was detected in five cases of B-chronic lymphocytic leukemia; five cases of splenic marginal zone lymphoma; six cases of nodal marginal zone cell lymphoma; two cases of gastric marginal zone cell lymphoma; or ten benign lymphoid infiltrates in bone marrow, spleen, or lymph nodes. In summary, although the total number of studied cases is small and a larger series of cases may be required to confirm our data, we present optimized immunohistochemical conditions for cyclin D1 in fixed, paraffin-embedded tissue that can be useful in distinguishing MCL and hairy cell leukemia from other small B-cell neoplasms and reactive lymphoid infiltrates.     

套细胞淋巴瘤的临床病理特征和细胞周期蛋白D1在诊断中的意义

目的 观察套细胞淋巴瘤的临床病理学特征及细胞周期蛋白D1染色在诊断中的意义。方法 对8例淋巴结套细胞淋巴瘤作临床病理观察及随访,LSAB法做免疫表型分析（CD45RO、CD5、CD20、细胞周期蛋白D1、Ki-67、bcl-2）。结果 患者年龄43-78岁（平均年龄57岁）,男女3：1。组织学特点为：（1）淋巴结结构破坏并被单一的淋巴样细胞所取代,淋巴细胞以套区增生性、结节性、弥漫性三种模式增生。（2）淋巴样细胞核有一定的不规则性,染色质中等致密,核分裂象少见,类似中心细胞。其中有3例转变为高度侵袭性的母细胞样变型。所有的病例都呈cyclinD1与bcl-2阳性、CD20阳性、CD45RO阴性、CD5阳性。结论 套细胞淋巴瘤有其特征的形态改变及免疫表型。根据组织病理学特征及cyclin D1阳性,可与其它类型的小B细胞淋巴瘤相鉴别。套细胞淋巴瘤的母细胞样变型也应当与其它变型区别。     

Role of p27Kip1 protein in the cell cycle and its appearance in lymphoid tissues, particularly non-Hodgkin's B-cell lymphomas. Review

Cell cycle progression is governed by cyclin dependent kinases (CDK) that are activated by cyclin binding and inhibited by CDK inhibitors. Protein p27Kip1 functions as a CDK inhibitor, which controls the progression from G1 to S phase. Further, p27Kip1 may have a positive regulative influence. In nonneoplastic tissues and in the majority of tumors investigated so far, the immunohistochemical positivity of p27Kip1 showed an inversely proportional relationship to the proliferation index. Among B-cell non-Hodgkin lymphomas, the exceptions to this rule are represented by mantle cell lymphoma, hairy cell leukemia, and the immunoblastic Epstein-Barr virus latent membrane antigen positive diffuse large B-cell lymphoma in AIDS patients. The loss of p27Kip1 expression is a negative prognostic factor in numerous tumors, including the majority of B-cell lymphomas.     

Mantle cell lymphoma lacking the t(11;14) translocation: a case report and brief review of the literature

The diagnosis of mantle cell lymphoma (MCL) requires a multifaceted approach with integration of morphology and immunophenotype, supported by cyclin D1 positivity or identification of t(11;14)(q13;q32). Interphase fluorescence in situ hybridisation (FISH) using a dual colour, dual fusion probe strategy for t(11;14) is a rapid test with high sensitivity and specificity for MCL, and is easily performed on routine bone marrow aspirate or peripheral blood specimens. This test has become the method of choice for many pathologists to confirm a diagnosis of MCL. This report describes a case of MCL with a normal (negative) FISH signal pattern for t(11;14) that was found to be cyclin D1 positive by immunohistochemistry in tissue sections. This case illustrates the need for additional testing when the t(11;14) abnormality is not identified but the morphology and immunophenotype are otherwise suggestive of MCL.     

Morphological spectrum of cyclin D1-positive mantle cell lymphoma: study of 168 cases

Immunostaining for cyclin D1 is essential for reliable diagnosis of mantle cell lymphoma (MCL). However, a small number of cyclin D1-positive lymphomas other than MCL have been encountered. Our goal was to investigate the morphological spectrum of MCL as a disease entity, based on cyclin D1 overexpression. We reviewed 181 biopsy specimens obtained from 168 cases of cyclin D1-positive MCL. Typical findings were the presence of nodular (53.9% of cases) or diffuse (46.1%) histological patterns, containing mantle zone patterns (16.8%), naked germinal centers (33.5%) and perivascular hyaline deposition (83.2%). Unusual findings of residual germinal centers with a mantle cuff (four cases) and follicular colonization (two cases) were seen. High magnification showed a monotonous proliferation of tumor cells with cytological diversity including small (3.0%), intermediate (43.1%), medium (34.1%), medium-large (13.2%) and large (6.6%) cells. Pleomorphic and blastic/blastoid variants were encountered in 9.6 and 7.2% of cases, respectively. Three cases had foci of cells of considerable size, with a moderately abundant pale cytoplasm resembling marginal zone B cells. Two cases showed an admixture of cells which appeared transformed and mimicked the histology of chronic lymphocytic leukemia/small lymphocytic leukemia. In one, neoplastic mantle zones were surrounded by sheets of mature plasma cells, resembling the plasma cell type of Castleman's disease. An admixture of areas characteristic of MCL and of other larger cells, indicating histological progression or a composite lymphoma, were observed in seven cases. In high-grade lesions of five cases, nuclear staining of cyclin D1 was rarely detected. In our experience, cyclin D1 expression was also found in nine lymphomas other than MCL (five plasma cell myelomas, three Hodgkin's disease and one anaplastic large cell lymphoma). The application of cyclin D1 staining prompted us to recognize the broad morphological spectrum of MCL. MCL can be diagnosed with the application of cyclin D1 immunostaining, if careful attention is given to architectural and cytological features.     

A biological role for deletions in chromosomal band 13q14 in mantle cell and peripheral t-cell lymphomas?

Structural aberrations of chromosomal band 13q14 are frequent in B-cell chronic lymphocytic leukemia (B-CLL) and target a putative tumor suppressor gene in the genomic region between the RB1 gene and the genetic marker D13S25. Recently, it has been suggested that alterations of this particular region might also be of relevance for the pathogenesis of mantle cell lymphomas (MCL). We applied dual-color fluorescence in situ hybridization (FISH) using probes for the RB1 and/or D13S25 loci and screened a total of 236 B- and T-cell non-Hodgkin's lymphomas (NHL) for deletions occurring in this genomic region. In MCL, the high rate (12/32; 38%) of hemizygous deletions and especially a deletion pattern similar to B-CLL in four of the cases provide further evidence that a substantial proportion of MCL cases may share a common way of pathogenesis with B-CLL. In other B-cell NHL, the frequency of allelic loss affecting 13q14 was overall low. However, the finding of 13q14 microdeletions in seven cases without detectable alterations of chromosome 13 at G-banding analysis might indicate a possible involvement of this genetic region also for the lymphomagenesis of single cases of B-cell NHL other than B-CLL and MCL. In T-cell NHL, allelic loss at 13q14 was encountered in three of 13 peripheral T-NHL, NOS. Taking into account the very limited cytogenetic data yet available in this entity, our series provides further evidence that 13q14 changes might represent one of the most frequent genetic abnormalities in T-cell NHL.     

Cyclin D1 over expression in malignant lymphomas

Cyclin D1, the regulatory subunit of certain protein kinases thought to advance the G₁ phase of the cell cycle, is now established as a protooncogene, with evidence indicating that its derangement may contribute to the uncontrolled cell growth characteristic of tumors. The chromosomal translocation t(11;14)(q 13 :q32), Involving rearrangement of the BCL-1 locus, is closely associated wlth human lymphoid neoplasia affecting mantle cell lymphomas (MCL). Recently, the putative BCL-1 protosncogene turned out to be none other than the cydin D1 gene. Although the observed break points In the BCL-7 locus are not tightly clustered, Its rearrangement has been documented In 40–70% of cases of mantle cell lymphoma, whereas it only rarely occurs in other B cell lymphomas. Of note, all of the known break points leave the cyclin D1 coding region structurally Intact and result In increased protein expression, implying that this may provide a highly sensitive and specific marker for MCL. Recent studies demonstrated that immunohistochemical detection In paraffin-embedded material, using a mone clonal antibody, Is very useful for routine diagnosis. Current knowledge of cydin D1 over expression In malignant lymphomas, with emphasis on its clinic pathologic significance, is reviewed.     

Prominent intrasinusoidal infiltration of the bone marrow by mantle cell lymphoma

Intrasinusoidal infiltration of bone marrow (BM) may accompany several malignant lymphoproliferative disorders. In small B-cell lymphomas, this pattern is considered specific for splenic marginal zone lymphoma (SMZL) when exclusive or prominent, although it may occur in other subtypes of non-Hodgkin's lymphomas (NHLs) as a minor feature. Here we report 2 cases of mantle cell lymphoma (MCL) with a prominent intrasinusoidal BM infiltration pattern. Both patients presented with massive splenomegaly and peripheral blood involvement characterized by markedly atypical lymphocytes, but no lymphadenopathy. The cytological features and the phenotype of the lymphoma cells were diagnostic of MCL. The malignant B cells showed coexpression of B-cell markers (CD20+ and CD79a+), CD5 antigen, and cyclin D1 by immunohistochemistry. We discuss the specificity of an intrasinusoidal growth pattern in the bone marrow, emphasizing the importance of using a broader immunohistochemical panel in the differential diagnosis of intrasinusoidal BM infiltration by NHL.