Plexiform Fibrohistiocytic Tumor on the Ear: Case Report and Immunohistochemical Investigation of Stromal Factor.

Plexiform fibrohistiocytic tumor (PFT) is a rare mesenchymal neoplasm of intermediate malignant potential with a high local recurrence rate. In this report, we describe a case of PFT on the ear, which showed a dense deposition of periostin (POSTN) in the stromal areas of the tumor. In addition, dense infiltration of CD163+CD206- tumor-associated macrophages (TAMs) was detected in the same areas as POSTN. Since POSTN was previously reported to possess immunomodulatory effects on TAMs, our present report suggested the significance of the POSTN/TAMs axis in the progression of PFT.