Follicular lymphoma of the spleen: multiparameter analysis of 16 cases.

Follicular lymphoma (FL) involving the spleen must be distinguished from reactive hyperplasia and from other lymphomas. A prior study reported that splenic FLs frequently lack BCL2 expression, further complicating diagnosis. We examined 16 cases of splenic FL, including 12 cases initially diagnosed at splenectomy. Two morphologic patterns were identified: one with architectural abnormalities (AA) and one with an extensive architectural preservation (AP) pattern. Newly diagnosed AP cases were associated with older age (P = .051) and grade 1 histologic features (P = .023). All cases displayed a CD10+/BCL2+ phenotype. Cytogenetics and FISH identified IGH/BCL2 or BCL6 translocations in all tested cases. Splenic FLs display phenotypic and cytogenetic findings similar to nodal FLs. However, splenic FLs frequently display an exclusively intrafollicular growth pattern resembling so-called in situ FL. Recognition of subtle FL with preserved architecture is important because patients may have overt FL at other sites or the FL may progress to overt nodal disease.