3.2.3 Dermatofibroma

Fibrous histiocytoma; sclerosing haemangioma; subepidermal nodular fibrosis; histiocytoma, histiocytofibroma; benign fibrous histiocytoma.

The dermatofibroma is a frequent, benign fibrohistiocytic dermal tumor. It may occur after an initial skin trauma (such as vaccination or insect bite) and is generally a firm, slow-growing lentil-shaped papule of pale or brownish colour.

Lesions present as solitary or multiple brownish, lentil-shaped, firm itchy papules. Pigmentation is often increased at the periphery.

Dermatofibromas are most often found on legs and upper extremities but can occur on the whole body except palms and soles.

Fibrous histiocytomas are benign fibrohistiocytic tumors. Most commonly, these tumors are located in the dermis and subcutis. They are made up of a mixture of fibroblastic and histiocytic cells, collagen and blood vessels. Variable hemosiderin, multinucleated giant cells, chronic inflammatory cells may be found in the lesions. Many variants have been described; more than one variant can be seen in the same lesion.

The histological features may include acanthosis or pseudoepitheliomatous hyperplasia of the overlying skin, a vague storiform pattern of bland spindle cells centred in dermis with possible extension to subcutis. The infiltration into and around fat cells is uncommon.

Some dermatofibromas present an atypical appearance on histopathological examination. These lesions are often in a phase of rapid growth or have reached a large size. They are often exophytic, globular or polypoid. Atypical features of the nucleus and cytoplasm are found and along with a number of mitoses. This is a pseudosarcoma-type presentation in which there is no risk of metastases.

Dermatofibromas have a chronic course and may remain unchanged or flatten with time. If left untreated, a dermatofibroma often stabilises in size and remains unchanged for a very long period of time.

Sometimes growing and itching may lead to scratching and superinfection.

Dermatofibromas are firm dermal papules that show a central depression when lateral pressure is applied to them (dimple-sign). Diagnosis is based on clinical features, and histology is rarely needed.

There is no need for treatment of dermatofibromas. However, some lesions may itch or may be at a site of the body skin where they are disturbing or may be continuously traumatized. A local corticosteroid injection can cause the lesion to regress. Surgical excision, cryosurgery or laser ablation can be performed.