Splenic follicular lymphoma: Clinicopathologic characteristics of a series of 32 cases

The spleen is frequently involved in B-cell lymphomas other than splenic marginal zone lymphoma. Here we describe a series of follicular lymphoma (FL) cases diagnosed in the spleen, consisting of 32 patients who presented clinically with splenomegaly, and slight or no peripheral lymphadenopathy. The splenic specimen had a micronodular pattern, germinal center cytologic composition, and frequent presence of marginal zone-like cells at the periphery of the nodules. Twenty cases showed absence or only partial/weak bcl2 protein expression, and 12 cases had homogeneous and strong positive bcl2 expression. The incidences of t(14;18)(q32;q21), CD10 expression, low histologic grade, and low proliferative index were significantly more frequent in FL bcl2-positive cases than in FL bcl2-negative cases. Splenic FL cases showed frequent relapses, with an overall survival of 55% at 5 years. No significant differences in survival were found between bcl2-negative and bcl2-positive cases. Splenic FL cases could be divided into 2 main variants: one was similar to classic FL with t(14;18) and CD10 expression, whereas the other was characterized by a higher proliferation index and histologic grade, and was more frequently diagnosed as a disease restricted to the spleen. Recognition of the distinct nature of these tumors should facilitate appropriate studies for determining the best therapy for such cases.