Cutaneous malignant ossifying fibromyxoid tumor.

A 76-year-old woman presented with a well-circumscribed 3 cm mass of her right buttock. The tumor, partially surrounded by a shell of woven and lamellar bone, had a lobular arrangement of highly cellular islands of tumor cells embedded in a variably fibrous to myxoid stroma. The lesional cells had well defined cytoplasmic membranes with varying amounts of clear to lightly eosinophilic cytoplasm. The nuclei exhibited moderate to severe nuclear atypia. Areas of tumor necrosis were present. The mitotic rate was 17 MF/50 high-power fields. The tumor was diagnosed as an ossifying fibromyxoid tumor (OFMT). OFMT is a rare tumor first described in 1989. Although OFMT usually occurs in deep soft tissue, up to 11% of reported lesions presented as cutaneous tumors. OFMT usually present in adults on the extremities or trunk. Most are histologically bland and apparently benign tumors, but OFMT with high nuclear grade, high cellularity, and >2 MF/50 high-power fields have shown potential for aggressive behavior including metastasis. OFMT with these features should be considered sarcomas. Given the histologic features, this tumor was considered a malignant OFMT. The patient had a wide excision. The patient died secondary to unrelated comorbidities without evidence of recurrence or metastasis.