A 62-year-old man presents with lymphadenopathy and peripheral blood lymphocytosis. Flow cytometry shows CD5-positive B cells, and lymph node biopsy reveals a monotonous population of small lymphocytes surrounding pale proliferation centers. Cyclin D1 is positive by immunohistochemistry. The underlying molecular event is:

• A t(14;18) causing overexpression of BCL2
• B t(11;14) causing overexpression of cyclin D1 ✓
• C Trisomy 12 with NOTCH1 mutation
• D Deletion of TP53 on chromosome 17p

Explanation

Mantle cell lymphoma is defined by t(11;14)(q13;q32), which brings the CCND1 gene under IgH enhancer control, producing nuclear cyclin D1 detectable by IHC. CLL/SLL shares CD5 positivity but lacks cyclin D1 expression, and trisomy 12 belongs to CLL cytogenetics, killing options C and D. t(14;18) defines follicular lymphoma, not a CD5-positive small A-cell neoplasm.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.