Sign of Leser-Trélat.

The sign of Leser-Trélat is rare. It is defined as the sudden eruption of multiple seborrheic keratoses caused by a malignancy. Because both seborrheic keratoses and cancer are common in the elderly, it is not always easy to tell from the literature or in any given patient if this sign is present. In fact, its validity has been questioned. Its association with malignant acanthosis nigricans is one of several of its features that support its legitimacy as a true paraneoplastic disorder.