Leser-Trelat sign

The Leser-Trélat sign is the explosive onset of multiple pruritic seborrheic keratoses, often with an inflammatory base. This can be an ominous sign of internal malignancy as part of a paraneoplastic syndrome. In addition to the development of new lesions, preexisting ones frequently increase in size and become symptomatic.

Although most associated neoplasms are gastrointestinal adenocarcinomas (stomach, liver, colorectal and pancreas), breast, lung, and urinary tract cancers, as well as lymphoid malignancies are associated with this impressive rash. It is likely that various cytokines and other growth factors produced by the neoplasm are responsible for the abrupt appearance of the seborrheic keratoses. In some cases, paraneoplastic acanthosis nigricans accompanies the sign of Leser-Trelat.