Primary cutaneous follicle center lymphoma with Hodgkin and Reed-Sternberg-like cells: a new histopathologic variant.

Primary cutaneous follicle center lymphoma (PCFCL) is the most frequent cutaneous B-cell lymphoma. A 62-year-old man presented with a solitary indolent subcutaneous nodule for 3 years duration, without other abnormalities. Histological examination showed lymphoproliferation with a nodular growth pattern characterized by fibrous collagen bands surrounding nodules. The nodules were composed of medium-sized centrocytes admixed with many large multilobulated and lacunar cells without eosinophils or granulomatous aspect. Hodgkin-like cells were CD30+, CD15+, PAX5+, OCT2+, BOB1+, MUM1+, Ki67+, Bcl6+ and focally CD20+ and EMA-, CD79a-, Bcl2- and CD10-. The medium-sized cells were CD20+, CD79a+, Bcl2+, Bcl6+ and CD10+, enmeshed in a network of CD21-positive follicular dendritic cells. Epstein-Barr virus detection was negative. Interphase fluorescence in situ hybridization showed the absence of BCL2 or BCL6 rearrangement. In such a case, the presence of Hodgkin-like cells intermixed with the tumor population may result in a pitfall diagnosis of classical Hodgkin lymphoma (CHL). Differential diagnoses to be ruled out are secondary or primary skin localization of rather CHL, or systemic follicular lymphoma. Several clinical, radiological, histological, immunohistochemical and molecular arguments indicated the diagnosis of PCFCL. To our knowledge, this is the first report of PCFCL with Hodgkin-like cells.