An Uncommon Case of Double-Hit Mantle Cell Lymphoma That Demonstrates a Transformation Process.

Objectives: Mantle cell lymphoma (MCL) is a mature B-cell lymphoma characterized by CCND1/IGH rearrangement. We reported a case of MCL harboring both CCND1/IGH and MYC/IGH rearrangements that also presented with an aggressive clinical course. Methods: Biopsy specimens were evaluated by morphological staining, immunohistochemistry, flow cytometry, conventional cytogenetics, fluorescence in situ hybridization (FISH), and next-generation sequencing (NGS). Results: Morphological and immunohistochemical staining of gallbladder samples demonstrated blastoid variant MCL. However, in the bone marrow sample, FISH indicated rearrangements in CCND1/IGH and MYC/IGH. Flow cytometry identified two groups of malignant lymphocytes. We sorted these two groups of cells. NGS then revealed that both cell types carried CCND1/IGH rearrangements and TP53 mutations. Furthermore, the CD19+/CD10+ cells carried additional MYC/IGH rearrangement and NOTCH2 mutation. Conclusions: The rearrangement of MYC and a mutation in NOTCH2 probably induced the transformation of MCL cells in this patient. This uncommon double-hit MCL case clearly demonstrates a transformation process.