Four Genetic Lymphoma-Specific Events (MYC, BCL2, BCL6 and CCND1) in High Grade B-Cell Lymphoma: Aggressive Mantle Cell Lymphoma or Cyclin D1-Positive DLBCL?

The term « double » or « triple hit lymphoma » is commonly used to describe mature B cell neoplasms with either BCL2 and/or MYC and/or BCL6 gene rearrangements. These rare and aggressive lymphomas with high Ki67 expression are categorized as « B-cell lymphomas unclassified, with features intermediate between diffuse B-cell lymphoma and Burkitt lymphoma » category in the WHO 2008 classification. To our knowledge, only 2 cases of lymphoma have been described with four specific genetic events (quadruple hit) involving MYC, BCL2, BCL6 and CCND1 genes (Bacher U. et al., Genes Chromosomes Cancer 2011). We describe here the third observation.

A patient, a 79 years old man, suffering from paraesthesias for 4 months, was admitted for polyneuritis in a context of poor general condition. Clinical examination showed the presence of numerous axillary, supraclavicular, mediastinal and inguinal lymphadenopathy, neuro-meningeal invasion and skin infiltration. The biopsy of a skin nodule of left arm revealed an infiltration consisting in large proliferating cells (Ki67 80%) stained by anti-CD20, BCL2 and BCL6 antibodies, but not with CD10 nor CD23, consistent with a diffuse large B-cell lymphoma (DLBCL), NOS diagnosis. Blood cell count showed 8.1 G/L leukocytes, 13.2 g/dL hemoglobin, 166 G/L platelets. LDH and β-2 microglobulin were elevated (989 U/I, and 9.14 mg/L respectively). Blood cell film examination showed the presence of 28% of pathological basophil lymphocytes (medium sized, with slightly clumped chromatin and frequent prominent nucleoli). Flow cytometry revealed that these cells expressed a monotypic lambda immunoglobulin light chain and were CD19, CD20, FMC7, CD22 positive, with a dim CD5 positivity and no CD10 staining. The negativity of CD23 associated to strong CD148 staining (Miguet et al, J Proteome Res2009) were in favour of the diagnosis of variant pleomorphic mantle cell lymphoma (MCL).

Cytogenetic study performed in the WBC found a complex hyperdiploid karyotype (47 chromosomes) with a t(3;22) translocation involving BCL6 and IGL genes, structural abnormality of a chromosome 8 resulting in juxtaposition of 5’MYC and BCL2 in FISH (with break of the MYC probe in FISH), a derivative chromosome 18 from a t(14;18) translocation with fusion of 5’IGH and BCL2, and a t(11;14) complex translocation involving IGH and CCND1 (54% of the nuclei). Overexpression of cyclin D1 was detected in the WBC by RQ-PCR, as well as in the skin lesion using immunochemistry. Others numeral (trisomy 12) and structural abnormalities (involving the 1, 7, 14 and 21 chromosomes) were also detected.

The patient was treated with a chemotherapy combining rituximab, ifosfamide, cytosine arabinoside and intrathecal methotrexate. He is still alive 5 months after the diagnosis.

This third case of quadruple hit lymphoma confirms the complexity of the classification of such aggressive malignancies. Initial rearrangement of the CCND1 gene characterizes MCL that may harbour in very rare cases additional rearrangements of MYC or BCL6. Conversely, cyclin D1 overexpression is considered a rare feature in DLBCL. Recently, Ok CY et al. (Cancer 2014) proposed to reclassify DLBCL with expression of cyclin D1 and CCND1 chromosomal rearrangement and CD5 positivity as aggressive pleomorphic MCL variant. But no case with rearrangement of 2 (or more) genes (BCL2 and/or MYC and/or BCL6) was described in this study.

Juskevicius D et al. (Am J Surg Pathol 2014) suggest the existence of a “gray zone” in which morphologic, clinical and genetic features are insufficient to segregate CD5- and SOX11-negative lymphomas with overexpression of cyclin D1/ translocation involving CCND1between blastoid MCL from cyclin D1-positive DLBCL.

In our case, immunophenotyping of circulating cells (CD5+, CD148++) as well as genetic and molecular features (translocation involving CCND1 and IGH, and overexpression of cyclin D1) allow us to diagnose a probable genetically unstable aggressive pleomorphic MCL variant with rearrangement of several extra genetic hits.