Adnexal tumours of the skin as markers of cancer-prone syndromes.

Adnexal tumours of the skin are benign, more rarely malignant, primary skin tumours that originate from, or differentiate towards, hair follicles, sebaceous and sweat glands. Although they are usually encountered as single, sporadic tumours, they may occasionally be multiple, hereditary; in that case, they may herald complex genetic syndromes that comprise visceral cancers. Dermatologists should be aware of these adnexal skin tumours, the diagnosis of which may contribute to an early detection of a cancer-prone syndrome with a potentially lethal outcome. The main tumours falling into this category and their associated syndromes are reviewed here.