Leser-Trélat (LT) sign (syndrome) is a rare, distinctive clinical phenomenon that is manifested by a sudden, eruptive, appearance of multiple itchy seborrheic keratoses (SK) that sometimes coincide with occult malignancy. A 73-year-old patient came for examination of numerous, large seborrheic keratoses (SK) on the skin. According to the patient's statement, SK did not occur suddenly and "eruptively". Nevertheless, ultrasound and endoscopic evaluation were suggested to the patient to exclude the Leser-Trélat phenomenon. The patient was then diagnosed with an occult, asymptomatic rectal neoplasm. The occurrence of numerous seborrheic keratoses (especially if they are "eruptive", large and bizarre in shape), should raise suspicion of LT phenomenon, or internal malignancy in the patient, and result in relevant diagnostic procedures to detect possible latent malignancy. It would be wise for the doctors of all disciplines to be acquainted with the existence of the LT sign (syndrome) and possible clinical implications of it.