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Skin - Nonmelanocytic tumors

Adnexal tumors

Adnexal tumors-general

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 2 July 2012, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.


● Usually differentiate only along one adnexal line, but there may be divergent differentiation within 1 or more tumors within the same patient

Algorithms (from Sternberg)

Cystic lesions:
(a) Glandular lesions are hidrocystoma (two rows of cells) or cutaneous ciliated cyst (cylindrical cells with cilia)
(b) Lesions with squamous keratinization are trichilemmal cysts, pilomatricoma, steatocystoma (sebaceous lobules in wall), vellus hair cyst (hair shafts in lumen), epidermoid cyst (contains lamellated keratin), dermoid cyst (adnexal structures in wall), trichofolliculoma (radiating immature hairs) or warty dyskeratoma (acantholytic dyskeratosis)

Basaloid tumors:
● Trichoepithelioma / trichoblastoma (ribbons of basaloid cells, cysts and fibroblastic stroma)
● Trichofolliculoma (mature and immature hair follicles)
● Cylindroma (jigsaw-puzzle appearance with thickened basement membrane)
● Spiradenoma (basaloid cells with 2 cell types)
● Sebaceous adenoma or carcinoma, eccrine poroma (large nodules connected to epidermis)
● Eccrine acrospiroma (large dermal nodules)
● Pilomatricoma (ghost cells)

Squamoid tumors:
(a) Solid lobules of eosinophilic cells are pilar sheath acanthoma (connected to crater-like cavity) or acrospiroma (not connected to crater-like cavity)
(b) Lobules with clear cells are acrospiroma (luminal differentiation), trichilemmoma (epidermal connection, peripheral palisading, thick basement membrane) or sebaceous tumors
(c) Lobules of squamous cells with central keratinization are proliferative trichilemmal tumor

Glandular tumors:
(a) Apocrine differentiation: papillary hidradenoma (papillary fronds, vulvar/perianal) or tubular apocrine adenoma (epidermal connection)
(b) Syringoma: small ducts with 2 rows of cells
(c) Papillary eccrine adenoma: cystic ducts and papillary fronds
(d) Papillated ducts open to epidermis: papillary syringadenoma (scalp) or nipple adenomatosis (nipple)
(e) Mixed tumor (chondroid syringoma): chondromyxoid stroma and tubular or anastomosing glands
(f) Sebaceous hyperplasia (lobular arrangement around a central duct), adenoma or carcinoma

End of Skin - Nonmelanocytic tumors > Adnexal tumors > Adnexal tumors-general

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