Myxoinflammatory fibroblastic sarcoma: a tumor not restricted to acral sites.

We report on nine new cases of myxoinflammatory fibroblastic sarcoma; in six of them the location of the tumor was distal (acral), and proximal in three (forearm, arm, and thigh). Tumors varied in size from 1.5 to 18 cm, were well-circumscribed, yellow-tan, and focally myxomatous. Histologically, they were similar in appearance and showed vaguely lobular architecture and oval, spindle, and epithelioid neoplastic cells with scattered, focally aggregated inflammatory cells. In all cases, in different numbers, bizarre giant cells with large, lobulated, or multiple nuclei were also admixed, some of them morphologically imitating Reed-Sternberg cells, lipoblasts, or ganglion cells; they showed distinct nucleoli or intranuclear inclusions. Myxoid areas were always present, to different extent. Immunohistochemically, tumor cells were uniformly positive for vimentin; some cells were also positive for CD68 and CD34. Ultrastructurally, tumor cells were nondescript, consistent with fibroblastic origin. On flow cytometry, two of the examined cases showed diploid pattern with low S-phase fraction. In none of the cases, metastases were observed, in one case the tumor recurred 5 years following surgery. We conclude that myxoinflammatory fibroblastic sarcoma is a distinct soft tissue tumor of low-grade malignancy and, until now, described only in extremities, although not confined to acral sites.