Plexiform fibrohistiocytic tumor

We report the case of a 6-year-old Japanese boy with a plexiform fibrohistiocytic tumor on the right perioral region. Clinically, the tumor, 5 mm in diameter, was a solitary, hard, erythematous, slowly growing, painless nodule. There was no preceding trauma. Histology revealed a well-circumscribed plexiform lesion with a biphasic appearance. Immuno-histochemistry demonstrated CD68 positivity in many of mononuclear macrophages. The lesion was negative for S-100 protein, lysozyme, CD57 and factor XIIIa. Interestingly, the tumor showed an intradermal location from superficial to deep dermis, and lacked osteoclast-like giant cells. During the follow-up for 9 months after the resection, there was no recurrence or metastasis.