A rare case of in situ follicular B-cell neoplasm involving sebaceous lymphadenoma.

In situ follicular neoplasia (ISFN) is characterized by a monoclonal proliferation of BCL2-positive B cells harboring the translocation t(14;18)(q32;q21). These cells are confined to follicle centers and are usually identified incidentally, with a very low risk of progression to follicular lymphoma. Sebaceous lymphadenoma is a rare, benign salivary gland tumor, most commonly arising in the parotid gland, and is histologically defined by solid epithelial nests and cysts with sebaceous differentiation in a hyperplastic lymphoid stroma. We report an unusual case of ISFN arising within a sebaceous lymphadenoma. To the best of our knowledge, this association has not previously been reported.