[Superinfected epidermal inclusion cyst of the thigh with development of squamous cell carcinoma--case report of a rare complication].

Epidermal cysts (atheroma) are the most common benign tumours of the skin with ubiquitous localisation all over the body. However, rupture of the atheroma and formation of an inclusion cyst with additional superinfections are frequently seen. Malignant transformations have rarely been reported. Presented here is the unusual case of a 65-year-old woman with multiple atheromas and a distinctive tumour of the upper limb. Imaging diagnostics showed malignant deformation. Contrary to the imaging findings the histological/microbiological examination showed an enormous superinfected and ruptured epidermoid cyst with multiple abscess formation in the ventral upper limb. Radical surgical restoration with salvage of the limb was frustrated because of honey-combed anterior soft tissue and the changing bacterial spectrum. After resection of the complete ventral compartment, remission was realised approximately. In the follow-up there was a recurring infection with spontaneous fistula formation that histologically impressed as a squamous cell carcinoma. After proximal ablation of the upper limb, total rehabilitation of the infection as well as the malignoma could be achieved.