Small cell lymphocytic variant of marginal zone lymphoma: A distinct form of marginal zone lymphoma derived from naive B cells as a cutaneous counterpart to the naive marginal zone lymphoma of splenic origin

Primary cutaneous marginal zone lymphoma most commonly represents an indolent form of cutaneous B cell lymphoma. However, epidermotropic marginal zone lymphoma, blastic marginal zone lymphoma and B cell dominant variants without isotype switching can be associated with extracutaneous dissemination. The presumptive cell of origin is a post germinal center B cell with plasmacytic features. In the extracutaneous setting, however, a naïve B cell origin has been proposed for a subset of marginal zone lymphomas, notably splenic marginal zone lymphoma. The author encountered 11 cases of atypical lymphocytic infiltration of the skin primarily occurring in older individuals with an upper arm and head and neck localization; there was a reproducible pattern of diffuse and nodular infiltration by small monomorphic-appearing B cells. Phenotypically, the infiltrate was one predominated by B cells exhibiting CD23 and IgD positivity without immunoreactivity for CD38 and there were either no plasma cells or only a few without light chain restriction. In cases presenting with a solitary lesion complete excision and/or radiation led to successful disease remission in all cases without recurrence or metastatic disease. Of three cases with multiple initial lesions, evidence of extracutaneous disease was seen in two cases and recurrence occurred in one case. No patients have died of lymphoma. Longer term follows up and additional cases are needed to determine if this subset of marginal zone lymphoma is associated with a worse prognosis. © 2018