Basal cell carcinoma arising within a giant dermatofibroma

Introduction
Dermatofibroma is a common benign cutaneous tumour with typical clinical and dermoscopic features. Giant dermatofibroma is a rare variation of the proliferation with a diameter larger than 5 cm. The association of basal cell carcinoma and dermatofibroma has been described in 13 cases, but none of them was related to a giant dermatofibroma.

Objective
To report the first case of basal cell carcinoma arising in a giant dermatofibroma with atypical clinical features.

Case report
A 70-year-old woman presented with a giant skin tumour of the left arm observed since she was 15 years old. Histopathological examination revealed features of extensive basal cell carcinoma overlying a dermatofibroma. There was no evidence of local recurrence or metastases within 24 months after surgery.

Conclusions
The risk of malignant transformation in an exaggerated reactive proliferation of the epidermis overlying a dermatofibroma seems to be very low. Aggressiveness of that type of basal cell carcinoma is probably the same as classic basal cell carcinoma.