Accessory spleen: differential diagnosis for lymphoma in autoimmune lymphoproliferative syndrome.

Mutations of Fas or, less frequently, Fas ligand genes result in a rare inherited lymphoid disorder called autoimmune lymphoproliferative syndrome (ALPS) in which lymphoma frequency is increased. We report on a patient with ALPS who had been splenectomized for giant splenomegaly and progressively developed a voluminous abdominal tumor. The histology of the removed tumor revealed that it was an accessory spleen exhibiting typical features of ALPS involvement, as shown by the presence of a large excess of CD3+CD4-CD8- T cells and plasma cells without a detectable monoclonal population. This observation highlights the lymphoma's differential diagnosis in this context.