Sebaceous carcinoma (21.5): oil red-O stain positive (need frozen section). Sometimes Bowenoid changes (oil red-O negative carcinoma) in the epidermis coexist with sebaceous carcinoma in the dermis. EMA positivity is useful if frozen section not available

Merkel cell tumor (26.7): small cell tumor (1.130) is almost always present also in the dermis, in addition to the epidermotropic cells. Sometimes Bowen’s disease can coexist, or the small cells enter the epidermis. Merkel cell carcinoma cells are usually positive for CK20 (perinuclear dot pattern) and neuron-specific enolase

Clear cell acanthoma (18.6): discrete clone of pale keratinocytes in a psoriasiform epidermis, positive for glycogen and keratin

Hidroacanthoma simplex (23.10): this is an eccrine poroma with Borst–Jadassohn features, and sweat ducts are present

Pagetoid dyskeratosis 164 (1.27) Epidermotropic adnexal carcinoma (23.13): rare

Epidermotropic metastatic carcinoma or melanoma: very rare. Usually carcinoma or melanoma cells within the epidermis imply that a neoplasm is primary, but in this case metastatic melanocytes or epithelial cells actually infiltrate the epidermis. This usually can only be diagnosed with certainty when more than one lesion is present, making it more apparent that the lesions are metastatic