METASTASIZING CELLULAR DERMATOFIBROMA - A REPORT OF 2 CASES

Two cases of metastasizing cellular dermatofibroma (cutaneous fibrous histiocytoma) are presented. The first patient, an 18-year-old man, ha d a nodule excised from his right upper thigh, He developed three loca l recurrences at 1.5, 2, and 2.5 years and metastasis to inguinal lymp h nodes. He underwent lung segmentectomies for metastases 1.5 and 4 ye ars later and was alive with no evidence of tumor at latest follow-up, which was 15 months after the last surgery. The second patient, a 33- year-old man, had a nodule removed from his right posterior neck. The tumor recurred 3 months later and was reexcised. Right cervical lymph node metastases were excised at 7 and 8 years. A year later, a right c ervical lymph node dissection yielded one positive node of 35, and mul tiple metastases were excised from the right lung. The patient was ali ve with lung metastases 6 years later, which was the latest follow-up. Grossly, both tumors were single 2 cm nonulcerated dermal-subcutaneou s nodules. Histologically, they were characteristic of cellular dermat ofibroma; they were composed of plump to spindled ''fibrohistiocytic'' cells arranged in a storiform pattern and had areas of hemorrhage, he mosiderin, and infiltration between dermal collagen bundles peripheral ly. Recurrences and metastases were histologically similar except that lung metastases were cystic. The alternative diagnosis of angiomatoid malignant fibrous histiocytoma was considered for these two cases but was excluded because the tumors were partly dermal, had a well-define d storiform pattern, and lacked large blood lakes, multinodularity, a fibrous pseudocapsule, and surrounding chronic inflammation, We conclu de that dermatofibromas can rarely metastasize. Risk factors for metas tasis may include relatively large size, high cellularity, and local r ecurrence. Judging from these two cases, metastasizing dermatofibromas behave in an indolent manner.