Acral myxoinflammatory fibroblastic sarcoma. Six cases of a new tumor entity

Acral myxoinflammatory fibroblastic sarcomas are low-grade sarcomas of the distal extremities,first described by Meis-Kindblom and Kindblom in 1998. In our series of six cases this sarcoma occurred in four men and two women aged 22-60 years (mean 42.8). The tumors measured 1-4 cm (mean 2.4) and were localized in the foot (two cases), finger (two), wrist (one), and upper arm (one). The patients had a short history of a painless mass (mean duration 3 months). The tumors were poorly circumscribed, and infiltrated the subcutaneous fat and in one case each also the dermis and musculature. Histological features of the tumors were a multinodular configuration with infiltrative margins, myxoid and fibrotic zones with hyalinized areas, moderately pleomorphic cells with large cells showing a prominent nucleolus and an inflammatory infiltrate consisting of lymphocytes and histiocytes. Two months after excision the tumor recurred locally in two cases; no metastases were observed. Differential diagnosis is especially necessary from inflammatory pseudotumors and more aggressive sarcomas.