Seborrheic Keratosis

Seborrheic keratoses were common, benign, pigmented epidermal tumors that typically developed after age 50 and were found on areas such as the trunk, neck, face, and arms. The etiology was not well-known, but factors like heredity, sunlight, and HPV were suggested, with genetic studies indicating somatic mutations in the FGFR3 gene as significant. These lesions were primarily of aesthetic concern, though they could mimic malignant tumors, necessitating biopsy for accurate diagnosis. The sudden eruption of multiple lesions, known as the sign of Leser–Trélat, could indicate an underlying malignancy, warranting careful follow-up. Various histological types existed, including acanthotic, hyperkeratotic, clonal, reticulated, irritated, and pigmented, each with distinct characteristics.