Dermatofibroma (histiocytoma, benign fibrous histiocytoma and sclerosing hemangioma). DFs are common benign dermal tumours present as firm, indolent, discrete, usually solitary dermal nodules few millimeters but occasionally 2 to 3 cm in diameter. They usually occur on the extremities of young adults, and rarely elsewhere. Most lesions are red, but they may be reddish-brown because of hyperpigmentation of the overlying skin. The lesions have an ‘iceberg’ effect in that they feel larger than they look. A characteristic feature of the the tumour that it dimples when it is squeezed. Some lesions seem to follow minor trauma or an insect bite. DFs usually persist indefinitely, although spontaneous involution has been observed.