The sign of Leser-Trélat is characterized by the sudden manifestation and rapid growth in size and number of multiple seborrheic keratoses, related to an underlying neoplasia. A 57-year-old man, with a 4-month progression of changes in bowel habit, complained of thin stools and occasional rectal bleeding; one year earlier, an increasing number of skin lesions suddenly appeared on his back. Colonoscopy revealed a circumferential lesion 13cm from the anal margin (Fig. 1) and the histopathologic study reported adenocarcinoma. Multiple dermal lesions appeared on the patient's back (Fig. 2); they were biopsied, and the reported result was seborrheic keratosis (Fig. 3).

Figure 1.

Colonoscopy showing a friable lesion with irregular edges, 13cm from the anal margin, with a histopathologic diagnosis of adenocarcinoma.

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Figure 2.

Dermal lesions on the back (seborrheic keratoses).

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Figure 3.

Biopsy of the lesions corroborating seborrheic keratosis.

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The sign of Leser-Trélat is defined as the abrupt appearance and rapid increase in size or number of multiple seborrheic keratoses associated with a cancer. The sudden presentation of a large number of pigmented seborrheic keratoses should alert the clinician to rule out other entities and associations with neoplasia. Diagnosis of the skin lesions is confirmed through biopsy.