FISH analysis revealed trisomy 12 in ∼80% of the interphase cells (yellow). Trisomy 12 is associated with atypical morphologic features including cleaved nuclei and/or increased numbers of prolymphocytes, bright CD20 expression, absence of CD23 and expression of FMC-7. In contrast to mantle cell lymphoma, "atypical" CLL is negative for t(11;14) and cyclin D1 expression. Patients with Trisomy 12 are stratified into an intermediate risk category.