The spleen was found to be infiltrated by a MCL; lymphocytes were positive for CD20, CD5, bcl2, negative for CD23 and CD10, had a low mitotic index (Ki-67: 5 to 10%), and showed a strong positivity for cyclin-D1 and a characteristic pattern of infiltration (Figure 4). This evidence concerns the gene CCND1 and mantle cell lymphoma.