Superficial acral fibromyxoma: a clinicopathological and immunohistochemical analysis of 12 cases of a distinctive soft tissue tumor with a predilection for the fingers and toes.

Aim: Superficial acral fibromyxoma (SAFM) is a rare soft tissue tumor, recently delineated and documentated as a separate entity. We report 12 cases of SAFM observed in our department from June 2004 to June 2010 and highlight pathological features and differential diagnosis.
Methods: Radiographic examination of the affected digit was performed in all patients. All the tumors were surgically excised under local anesthesia. Follow-up was made every 6-8 months for a maximum period of five years.
Results: The patients consisted of 8 men and 4 women, age range 28-76 years (mean 51), presenting with a solitary mass or nodule located in the toes and fingers. Histologically the lesions were well circumscribed dermal nodules composed of stellate and spindle cells, arranged in a myxoid matrix. Very low grade atypia and a few mitotic figures were found in only one case. Neoplastic cells showed immunoreactivity for CD34 (12 patients). In contrast focally positive or negative staining was shown for the epithelial membrane antigen (EMA) and CD 99. Actin, S100 protein, HMB45 and cytokeratin were negative. In three cases marked hyperkeratosis and acanthosis of the epidermis was present. Pathological analysis confirmed the diagnosis of superficial acral fibromyxoma. No recurrences were observed even in a long term, 2-5 year follow-up.
Conclusion: Complete surgical excision of the tumors and a careful follow-up is suggested, despite the benign course previously reported.