Congenital Bednar's tumour

Bednar's tumour (BT) is a rare variant of dermatofibrosarcoma protuberans (DFSP). In addition to the typical histological findings of DFSP, melanin-containing dendritic cells are found in BT. Its occurrence at birth is very rare and there have been only two case reports of congenital BT in the English literature. A 12-year-old boy presented with a single, dome-shaped erythematous nodule, 25 × 15 mm in size, on the lower back. The lesion was present as a depressed patch at birth. Subsequently the lesion grew gradually to a dome-shaped mass. Histopathological examination found a dense infiltration of spindle cells arranged in a storiform pattern in the dermis, with pigmented cells admixed with the spindle cells. Cell mitosis and atypia were rarely seen. On immunohistochemical study, the tumour cells were positive for CD34 and melanin-containing cells were positive for S-100. A diagnosis of BT was made and the mass was removed by wide local excision. There was no evidence of recurrence at follow-up 8 months later.