KELOIDAL DERMATOFIBROMA - REPORT OF 10 CASES OF A NEW VARIANT

Dermatofibroma is a common cutaneous tumor. Unusual variants of dermat ofibroma that exhibit various epidermal changes or different cellular composition have been described. We observed 10 cases of a novel varia nt of dermatofibroma characterized by keloidal change within the tumor . Formalin-fixed, paraffin-embedded tissues were used for histochemica l and immunohistochemical studies. The patients consisted of six women and four men; median age was 34 years (17 to 59 years). All tumors oc curred on the extremities, and six were present for at least 2 years. Tenderness was mentioned in four cases. They were described as erythem atous or brown papules 1 cm or smaller. Clinical appearance did not de viate from that of ordinary dermatofibromas. Microscopically, the exci sed tumors showed a superficial circumscribed area of keloidal change under an atrophic epidermis in an otherwise ordinary dermatofibroma. I n the keloidlike area, multinucleated giant cells, hemorrhage, hemosid erin deposits, and scattered KiM1P-positive histiocytes, but not facto r XIIIa-positive or CD34-positive cells were present among the thick c ollagen fibers. There were no known recurrences. This variant dermatof ibroma should not be overlooked as a simple keloidal scar. The observa tion of keloidal change in dermatofibromas may support the connotation that trauma is a possible cause of dermatofibroma. The fact that Asia n people are more prone to develop keloid may have led us to find this new variant.