Seborrheic keratosis

Seborrheic keratosis is a common, noncancerous skin growth that usually appears as a brown, black, or light tan patch on the skin. It primarily affects the epidermis, the outer layer of the skin, and is most often seen in older adults. These growths can vary in size and have a waxy, stuck-on appearance. Although they are harmless and do not cause pain, they can sometimes become irritated or itchy. The condition mainly affects the skin system and does not spread or turn into skin cancer. People often notice these spots on the face, chest, shoulders, or back. The presence of multiple lesions is typical and usually increases with age.

Seborrheic keratosis is a benign epidermal tumor characterized by the proliferation of immature keratinocytes leading to well-demarcated, pigmented, verrucous plaques. It arises due to clonal expansion of epidermal keratinocytes with mutations often involving the FGFR3 and PIK3CA genes. The lesions are typically asymptomatic and develop gradually, predominantly in middle-aged and elderly individuals. Histologically, they show hyperkeratosis, acanthosis, and horn cysts. The condition is clinically significant as it can mimic malignant lesions such as melanoma, necessitating differentiation. It is not associated with systemic disease or malignancy but may be cosmetically concerning. The pathogenesis involves both genetic and environmental factors, including sun exposure.