Cytogenetic analysis of mantle cell lymphoma (MCL), characterized by the presence of t(11;14)(q13;q32) translocation, is often difficult because of the low proliferating rate of MCL cells and the presence of normal cells in bone marrow which may interfere with growth of MCL cells. We describe herein a TPA (12-O-tetradecanoylphorbol 13-acetate) stimulated culture to improve detection of t(11;14)(q13;q32) in 20 MCL patients regardless of the samples used.