Calcifying aponeurotic fibroma: A clinicopathologic study of 22 cases arising in uncommon sites

Calcifying aponeurotic fibroma is a rare soft tissue tumor that primarily occurs in children and adolescents and has a strong predilection for the distal portion of the extremities, especially the hands and feet. This report describes 22 previously unpublished cases arising in uncommon sites. Fifteen patients were male, and seven were female (age range, 2 to 43 years; median age, 9 years). The process typically presented as a painless mass and was present from 2 weeks to 11 years before resection. Sites of involvement were the back (n = 8), knee region (n = 5), thigh (n = 3), forearm (n = 3), elbow (n = 2), and arm, not otherwise specified (n = 1). The lesions were often adherent to dense fibrous connective tissue (eg, tendon, fascia, or periosteum) and ranged from 1.0 to 5.0 cm in maximum dimension. The process typically had an irregular contour and a firm, fibrous consistency. Sometimes minute foci with a calcific appearance were evident grossly. Microscopic examination showed spindled fibroblasts with a fascicular growth pattern and scattered epithelloid cells bordering chondroid foci with or without mineralization. Immunoreactivity was present for vimentin (six of six), muscle-specific actin (three of six), smooth muscle actin (three of six), CD99 (five of five), CD34 (one of six), CD57 (one of six, trace), EMA (two of six, trace), 5100 protein (five of six), CD68 (five of five), and progesterone receptor (one of six). The tumors were managed by local excision (n = 20), incomplete local excision (n = 1) and biopsy only (n = 1). Follow-up information was available for 10 patients with a median follow-up interval of 94 months. Five patients (50%) developed one or more recurrences. Familiarity with this entity should help to avoid confusion with other processes, including infantile and extraabdominal fibromatoses, a chondroma of soft parts, and a fibrous hamartoma of infancy.