Steatocystoma simplex. A solitary steatocystoma.

Steatocystoma simplex, an entity not previously described, to my knowledge, occurred in 16 women and 14 men. Eleven cysts were situated on the face, six on the limbs, and five on the chest. The clinical diagnosis was usually some type of cyst. The lesions contained yellow fluid. Microscopic findings showed a partially collapsed, thin-walled cyst lined by stratified squamous epithelium with a thick, undulating hyaline cuticle and sebaceous glands in or near the wall. When compared with steatocystoma multiplex and dermoid cysts, the differential features of steatocystoma simplex included its solitary nature, occurrence in adulthood, lack of family history, and intracutaneous location. Just as other dominantly inherited syndromes of multiple benign adnexal tumors, such as cylindromas, trichoepitheliomas, and trichilemmomas, have their counterparts in nonheritable solitary tumors, so steatocystoma multiplex has its parallel in steatocystoma simplex.

Pilar sheath acanthoma.

A newly recognized, benign follicular tumor occurred in nine patients who ranged in age from 46 to 75 (median, 55) years. The neoplasms were solitary, asymptomatic, skin-colored nodules with a central pore-like opening plugged with keratin. All lesions had been present for years. Eight were on the skin of the upper lip and one was on the forehead. Histologically, a central cystic cavity showing epidermoid keratinization extended from the surface into the deep cutis. Multiple tumor lobules that were composed of hair sheath epithelium extended from the cyst wall into the surrounding corium. This neoplasm, which we have named "pilar sheath acanthoma," must be differentiated from trichofolliculoma and dilated pore.

Halo congenital nevus.

A 24-year-old woman noted a depigmented halo around a pigmented lesion that had been present on her abdomen since birth. The halo and the central pigmented zone showed no change during the following year. Light and electron microscopic studies disclosed an uninflamed nevus extending to the deep reticular dermis; peripherally, the basal layer of the epidermis was depigmented. These findings indicate that a halo may develop about an uninflamed nevus that does not involute, and that the nevus may show the specific histopathology of congenital nevus.

Desmoplastic malignant melanoma.

A 68-year-old man sought dermatologic attention for a tumor of the arm. Biopsy specimen showed abnormal, essentially amelanotic, spindle-shaped cells in the cutis, greatly fibrotic stroma, and focal epidermal invasion. Desmoplastic malignant melanoma was diagnosed. The lesion was widely excised and axillary lymphadenectomy performed; one node showed metastasis. Nine months later, he died with widespread metastatic disease. To our knowledge, this is the first report of this entity since its delineation in 1971 and the only case in which diagnosis was established on initial biopsy and followed by definitive therapy. Desmoplastic melanoma has been confused with benign fibrosis, invasive fibromatosis, and fibrosarcoma, and is another example, with morpheaform basal cell carcinoma and sclerodermoid metastatic lesions from breast carcinoma, in which desmoplastic stroma may obscure the epithelial nature of cutaneous neoplasm.