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Skin - Nonmelanocytic tumors

Adnexal tumors-hair follicles

Keratinous cyst


Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 29 June 2012, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Most probably arise from infundibular portion of hair follicles
● Clinically called (incorrectly) sebaceous cyst
● Lesions of palm, sole or other sites may contain HPV 57 or 60
● Cysts contain keratin and lipid debris from sebaceous secretions
● Cysts may be painful if ruptured


Epidermal (epidermoid) type

General
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● Also called infundibular cyst
● Lined by keratinized epithelium with distinct granular layer, contain lamellated keratin but no calcification
● May have seborrheic keratosis-like changes in cyst wall

Micro images
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Follicular cyst (infundibular type)


Trichilemmal (pilar) type

General
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● Also called isthmus-catagen cyst or a “wen”
● Often on scalp, has trichilemmal-type keratinization (sudden keratinization without a granular layer), uneven boundary between keratinized and non-keratinized cells
● Non-lamellated keratin within the cyst, often with nucleated cells, often calcified

Micro images
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Trichilemmal type

End of Skin - Nonmelanocytic tumors > Adnexal tumors-hair follicles > Keratinous cyst


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