Many seborrheic keratoses on the back of a person with Leser–Trélat sign due to colon cancer.
The Leser-Trélat sign is the explosive onset of multiple seborrheic keratoses (many pigmented skin lesions),:638 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. 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.