Calcifying fibrous pseudotumor.

We report 10 cases of a distinctive benign fibrous lesion characterized by the presence of abundant hyalinized collagen with psammomatous or dystrophic calcifications and a lymphoplasmacytic infiltrate. The lesions were present from 2 months to 10 years before resection and ranged in size from 2.5 to 15 cm. They involved subcutaneous and deep soft tissues and, although relatively well-circumscribed, occasionally infiltrative borders or entrapped structures were seen on microscopic examination. The lesions were located in the extremities (three cases), trunk (two cases), scrotum (two cases), groin (one case), neck (one case), and axilla (one case). Both sexes were equally affected. The mean and median ages of the patients were 16.2 and 18.5 years, respectively (range, 1 to 33 years). All cases were initially managed by simple local excision. Follow-up ranging from 2 months to more than 10 years (median, 41.5 months) was available in six cases and revealed a local recurrence in one instance; this became clinically apparent about 7.5 years after the initial resection. Morphologic features and follow-up data suggest this may be a unique form of fibrous pseudotumor.