The Leser-Trélat sign is a well-known skin manifestation of internal malignancy, depicting the rapid growth of multiple seborrheic keratoses (SKs), and often associated with insistent itching. Our Case 1 presented with multiple SKs and a bladder cancer lesion measuring 4 cm in diameter which was detected by contrast computed tomography. In Case 2, which had relatively few SKs but intense itching, upper endoscopy revealed gastric cancer in situ. Case 3 complained of rapidly increased SKs. He had already undergone the endoscopic excision of a bladder cancer lesion. Typical regular arrangements of SKs were recognized in our cases, appearing either like a Christmas tree or like raindrops on the back in Case 1, as well as resembling splashing water on the abdomen in Case 2. Such characteristic SK distribution strongly suggested the involvement of epidermal growth factors, such as transforming growth factor-α, originating from internal cancer, which enabled us to detect cancer at an early stage, even in Case 2, in whom only a few SKs were present. Though internal cancers associated with Leser-Trélat sign cases are mainly located in the intestinal tract and are detectable by upper/lower endoscopy, previous reports indicate that almost all parts of the body can become affected areas. As a result, we found computed tomography, especially contrast computed tomography, to be very useful for identifying internal malignancies in any parts of the body.
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