Dermatofibromas on the Foot and Ankle: A Clinicopathologic Characterization of 31 Cases.

Background: Dermatofibroma (DF) is a common benign soft-tissue tumor. It occurs anywhere on the body but is commonly seen on the upper and lower extremities. It is frequently found in young to middle-aged adults and predominantly in females.

Methods: Thirty-one patients with DF on the foot and ankle diagnosed and treated during a 6-year period were characterized.

Results: The patients (16 males, 15 females) were aged 7 to 75 years (average, 55 years). Clinically, 17 patients noted painful symptoms, and 14 were painless. Grossly, DF manifested as a raised red, pink, tan, or skin-colored soft mass. The tumor size ranged from 0.3 to 1.5 cm (average, 0.67 cm in diameter). Twenty-six DFs (84%) were localized on the dorsal surface of the foot and ankle, and five (16%) were found on the plantar aspect. Eighteen patients were treated by surgical excision of the tumor (>0.5 cm), and 13 patients had observational follow-up after punch biopsy due to the small size (≤0.5 cm) and benign nature of these lesions. Further follow-up found that only one patient (3.2%) had a local recurrence, 37 months after surgical excision, which was completely reexcised. Histologically, DF is characterized by proliferation of spindle fibroblasts and histiocytes, in a vague fascicular pattern, and thickened collagen bundles.

Conclusions: Dermatofibroma on the foot and ankle predominantly occurs in patients in their 50s, without a preponderance by sex. It needs to be differentiated from other benign and malignant tumors with histologic analysis and immunostaining with factor XIIIa, CD68, and other biomarkers. Treatment options include either surgical excision or observational follow-up after biopsy, depending on the clinical characteristics and effect on functional activity.