Immunophenotypic variations in mantle cell lymphoma.

Mantle cell lymphoma (MCL) expresses pan-B-cell antigens and is usually CD5+/CD10-/CD23-/FMC7+. In this study, we evaluated 52 patients with confirmed diagnoses of MCL and identified variant immunophenotypes in 21 patients (19/48 classical and 2/4 variant MCLs), including CD5- in 6 (12%) of 52, CD10+ in 4 (8%) of 50, CD23+ in 10 (21%) of 48, and FMC7- in 4 (11%) of 37 cases. Three cases showed variations in 2 antigens, including CD5-/CD23+, CD10+/FMC7-, and CD23+/FMC7-; they were all classical MCLs. One blastoid variant MCL was CD23+, and one was FMC7-. Evaluation for proliferation index by immunohistochemical analysis for Ki-67 demonstrated no significant difference between MCLs with variant immunophenotypes and MCLs with typical immunophenotypes. The high proliferation index (>60%) was exclusively seen in the blastoid and pleomorphic variants. Our results indicate that immunophenotypic variations are common in MCL, and recognizing the variability is important for accurate subclassification of B-cell lymphoma.