Irritated seborrheic keratosis (also known as inverted follicular keratosis). A, Low-magnification photomicrograph shows a papillary epidermal proliferation with hyperkeratosis on the surface. Clinically, this lesion appeared as a cutaneous horn. B, High-magnification photomicrograph of a different lesion. The epidermis often shows whorls of cells, known as squamous “eddies” (arrows), and mild disorganization.