Primary Cutaneous Follicle Center Lymphoma.

CONTEXT.—: Primary cutaneous follicle center lymphoma is a low-grade B-cell lymphoma that is limited to the skin at diagnosis. It has a differential diagnosis that includes systemic/nodal follicular lymphoma secondarily involving the skin; primary cutaneous diffuse large B-cell lymphoma leg type; reactive lymphoid hyperplasia; and primary cutaneous marginal zone lymphoma. OBJECTIVE.—: To review the clinical, morphologic, immunophenotypic, and genetic features of primary cutaneous follicle center lymphoma; its differential diagnosis; and the evidence that supports use of immunohistochemistry and genetic testing in the diagnosis and prognosis of this entity. DATA SOURCES.—: Pertinent literature regarding cutaneous B-cell lymphomas is summarized and University of Michigan cases are used to highlight characteristics of primary cutaneous follicle center lymphoma. CONCLUSIONS.—: Primary cutaneous follicle center lymphoma is a low-grade B-cell lymphoma with distinctive features, although some cases may have elements that overlap with other lymphomas, complicating interpretation.