Fig. 91.1 Folliculo-sebaceous-apocrine unit and eccrine sweat gland. Adnexal tumors showing differentiation toward the hair follicle, sebaceous gland, apocrine gland, and eccrine gland are listed in correspondingly colored boxes. Important entities are in capital letters; entities associated with syndromes are in italics (see Tables 91.1–91.3). *Can show germinal differentiation; **differentiation toward entire follicle.

Cysts (e.g. epidermoid and pilar) are discussed in Chapter 90. BHD encodes folliculin, a tumor suppressor; CYLD encodes a deubiquinating enzyme; APC encodes a protein that regulates cell adhesion/migration.

Cysts (e.g. hidrocystoma) are discussed in Chapter 90.

Fig. 91.2 Pilomatricoma. A nodule on the cheek of a child.

Fig. 91.3 Trichofolliculoma. Wispy vellus hairs emerge from a skin-colored papule with a dilated central pore.

Fig. 91.4 Fibrofolliculomas in association with Birt–Hogg–Dubé syndrome. A Several skin-colored papules are present on the ear. B Multiple smooth papules of the lateral cheek that are relatively hypopigmented and lack the telangiectasias of the background skin.

Fig. 91.5 Tumor of the follicular infundibulum. Multiple hypopigmented thin papules on the cheek.

Fig. 91.6 Multiple familial trichoepitheliomas. Numerous skin-colored papules and nodules on the mid-face.

Fig. 91.7 Sebaceous hyperplasia. Skin-colored to yellowish papules with a central dell.

Fig. 91.8 Syringomas. A Aggregated skin-colored papules on the eyelids. B Multiple skin-colored to pink, smooth papules on the neck and upper chest. The lesions favor the ventral surface of the trunk, a distribution pattern referred to as ‘en demicuirasse’. B, Courtesy, Jean L. Bolognia, MD.

Fig. 91.9 Mixed tumor (chondroid syringoma). Nodule on the chin. Courtesy, Ronald P. Rapini, MD.

Fig. 91.10 Poroma. A biopsy specimen is necessary to establish a definitive diagnosis.

Fig. 91.11 Hidradenoma. A solitary violaceous nodule on the abdomen with serous drainage.

Fig. 91.12 Syringocystadenoma papilliferum. Grouped papules and nodules. The possibility of an associated nevus sebaceus needs to be considered.

Fig. 91.13 Cylindroma. Whereas numerous tumors aggregated on the scalp are called turban tumors, solitary lesions usually present as smooth erythematous nodules.

Fig. 91.14 Microcystic adnexal carcinoma. This tumor presents as a slowly expanding, firm plaque.

Fig. 91.15 Approach to multiple facial papules. As a general rule, multiple lesions are suggestive of a syndrome, but exceptions are syringoma and tumor of the follicular infundibulum (rarely syndromic). Other causes of multiple facial papules include BCCs, miliary osteomas, milia, verrucae, and acne. MEN, multiple endocrine neoplasia.