How is morphology of seborrheic keratosis?

➢ Round, exophytic, coinlike plaques that vary in diameter from millimeters to centimeters and have a “stuck-on” appearance ➢ They are tan to dark brown and have a velvety- to granularappearing surface. ➢ Occasionally, their dark color is suggestive of melanoma, leading to surgical removal. ➢ Microscopically, composed of monotonous sheets of small cells that resemble the basal cells of the normal epidermis ➢ Variable melanin pigmentation is present within these basaloid cells, accounting for the brown coloration seen grossly. ➢ Hyperkeratosis occurs at the surface, and the presence of small keratin-filled cysts (horn cysts) and downgrowth of keratin into the main tumor mass (pseudo–horn cysts) are characteristic features.