The Leser-Trélat sign is the explosive onset of multiple seborrheic keratoses (many pigmented skin lesions), 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.
^Odom, Richard B.; Davidsohn, Israel; James, William D.; Henry, John Bernard; Berger, Timothy G.; Clinical diagnosis by laboratory methods; Dirk M. Elston (2006). Andrews' diseases of the skin: clinical dermatology. Saunders Elsevier. p. 638. ISBN0-7216-2921-0.
^Yaniv R, Servadio Y, Feinstein A, Trau H (March 1994). "The sign of Leser-Trélat associated with transitional cell carcinoma of the urinary-bladder--a case report and short review". Clin. Exp. Dermatol.19 (2): 142–5. doi:10.1111/j.1365-2230.1994.tb01143.x. PMID8050144.