Myxoinflammatory fibroblastic sarcoma of the scalp: aggressive behavior at a rare, nonextremity site.

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare low-grade malignant soft tissue neoplasm, which usually presents on the distal extremities of adults and sometimes children. It has a characteristic appearance, of a lobulated or multinodular neoplasm of moderately atypical epithelioid or spindled cells, vacuolated cells, and enlarged or bizarre cells with macronuclei, with prominent mixed inflammatory infiltrate, and variably myxoid stroma. However, the proportions of each component vary, making diagnosis difficult, particularly when tumors arise at unusual nonextremity sites. We describe a case of MIFS occurring as a primary neoplasm on the scalp of an 80-year-old male, which recurred locally after 2 years and developed extensive bilateral cervical lymph node metastases. MIFS is exceptionally rare in the head and neck, and it has been described only once on the scalp. This case showed classical histologic features, and additionally a high mitotic index and atypical mitoses, which may be suggestive of a poorer prognosis. This case highlights the need to consider MIFS in the differential diagnoses of pleomorphic tumors of the head and neck, and it adds to the small number of MIFS showing highly aggressive behavior.