A typical immunophenotyping report by flow cytometry and immunohistochemistry report on tissue biopsy of MCL will be positive for CD5 (a T‐cell‐associated antigen), CD20, CD19, FMC7, sIgM/sIgD, CD22, CD79b and strongly Cyclin D1, and negative for CD23 (a key cell surface molecule for B‐cell activation and growth) and CD10 (a germinal centre‐associated antigen). The gene discussed is CCND1; the disease is mantle cell lymphoma.