[Retroauricular dermatofibroma in a child simulating a malignant tumour]

Dermatofibroma represents one of the commonest benign soft tissue tumours, and its diagnosis is usually straightforward if classical clinicopathologic features are evident. It occurs frequently on the extremities and trunk, often in young adults during the 3(rd) and 4(th) decades. We report a peculiar case of an aggressive cellular dermatofibroma in a child that simulated a malignant tumour. Our aim is to discuss the differential diagnosis.

An 8-year-old boy presented with a retroauricular tumour. Clinically, the lesion, 2 cm in diameter, was located in the left retroauricular region. It was nodular, erythematous, infiltrating the underlying tissue with an anterior spread leading to an amputation of the auricular lobule and a retraction of the tragus. Computerized axial tomography revealed a local tissular thickening extending in soft tissues without any bone involvement. A malignant lesion was initially suspected. A biopsy was performed. It was followed by a surgical resection. The lesion had the full microscopic characteristics of a cellular dermatofibroma.

Dermatofibroma is one of the major differential diagnosis of nodular cutaneous tumours in children that simulate malignancy. Histologic examination with immunohistochemical study is essential for diagnosis.