Abstract

We present a case of a 70-year-old African American male with a history of prostate cancer who  presented with a solitary, postauricular plaque. The biopsy specimen revealed a dense dermal infiltrate under a distinct Grenz zone. The infiltrate was composed of intermediate to large cells with centroblastic morphology and admixed centrocytes. Immunostains showed that infiltrate was positive for CD20, BCL6, weak CD10 and BCL2. MUM1 expression was seen in a small subset of lymphoma cells (~10%). Ki-67 proliferation was about 50%. CD21 highlighted weak dendritic meshwork in the background. Imaging indicated no systemic involvement and a diagnosis of primary cutaneous follicle center lymphoma (PCFCL) was made. Local radiation therapy was employed and the patient remained disease free for the next 17 months. Recently, the patient redeveloped the lesion at the same site with similar morphology and immunophenotype. Due to reported night sweats, a bone marrow biopsy and aspiration with flow cytometry were performed that showed no evidence of lymphoma. This is an interesting case of PCFCL that showed CD10 and BCL2 expression, typically seen in systemic follicular lymphoma. The morphology of PCFCL can be misleading with diffuse growth, large cells and high Ki-67, as seen in our case. MUM1 expression in a subset of tumor cells was also unusual and raises consideration for transformation. However, overall indolent course favors against it and highlights the importance of clinicopathologic correlation in the diagnosis of cutaneous lymphomas.