Case of primary cutaneous peripheral T-cell lymphoma, not otherwise specified, with characteristics of follicular helper T cells.

We report a case of an 88-year-old woman with a decalvant, erythematous, ulcerated tumor extending from the right temporal to occipital region. Histopathological analysis revealed a dense infiltration of medium-to-large-sized atypical cells throughout the entire dermis. The result of immunohistochemical analysis showed that the infiltrating T cells expressed programmed death-1 (PD-1), Bcl-6 and CXCL13. Flow cytometry analysis showed that CD4(+) PD-1(hi) T cells also expressed CD10, inducible T-cell co-stimulator and CXCR5. On the basis of the clinical appearance and the histopathological findings, we diagnosed the patient with primary cutaneous peripheral T-cell lymphoma, not otherwise specified. Recently, the concept of primary cutaneous follicular helper T (TFH)-cell lymphoma was proposed, and in this case, tumor cells clearly expressed TFH-cell markers. Therefore, we considered this case to be a variant of the entity. Although this entity is still provisional, this case supports the new concept.