[Dermatofibroma. A clinico-pathologic classification scheme].

Dermatofibroma is a common benign fibrohistiocytic lesion which presents with a wide variety of clinicopathologic variants. This may cause great difficulties in delineation from a variety of benign and malignant tumours. According to their peculiarities we differentiate: 1. Dermatofibromas with architectural peculiarities like deep penetrating, atrophic, giant, aneurysmal ("angiomatoid"), haemangiopericytoma-like, palisading or ossifying variants. 2. Dermatofibromas with cellular/stromal peculiarities like clear cell, granular cell, myofibroblastic, sclerotic, monster cell, atypical ("pseudosarcomatous"), elusive ("haemosiderotic"), cholesterotic, and myxoid variants. 3. Dermatofibromas with architectural and cellular/stromal peculiarities in homogenous arrangement like epithelioid cell, cellular benign variants, with smooth muscle proliferation, basal cell carcinoma-like, pseudolymphomatous, multinucleate cell angiohistiocytoma, cellular neurothekeoma, plexiform fibrohistiocytic tumour, plexiform xanthoma and plexiform xanthomatous tumour. 4. Complex or composite dermatofibromas with two or more architectural and cellular/stromal peculiarities in inhomogenous arrangement, e.g. silhouette of an epithelioid cell histiocytoma with plexiform fascicles of cellular neurothekeoma and granular cell features.