We report a case of a 39-year-old woman with a recurrent aneurysmal fibrous histiocytoma of the right lower leg. Cytogenetic analysis of the tumor specimen disclosed a 46,XX,t(12;19)(p12;q13) karyotype. Multicolor fluorescence in situ hybridization (M-FISH), followed by conventional FISH analysis, confirmed the reciprocal translocation as the sole cytogenetic anomaly, and allowed for the positioning of chromosomes 12 and 19 breakpoints proximal to the BCL3 gene and between ETV6 and PIK3C2G gene loci, respectively. Our case highlights the importance of distinguishing this recurrent but benign lesion from similarly appearing malignant skin tumors. Cytogenetic analysis may contribute to the diagnosis of this uncommon but distinctive clinicopathological entity.

Dermatofibroma. A clinico-pathologic classification scheme.Pathologe. 1998 Nov;19(6):412-9.

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.