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Skin - Nonmelanocytic tumors

Adnexal tumors-hair follicles

Keratinous cyst

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 11 June 2014, last major update June 2012
Copyright: (c) 2001-2014, PathologyOutlines.com, Inc.


● 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


● 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

Case reports

● 53 year old man with chest wall "sebaceous cyst" (Case of the Week #315)

Micro images

Follicular cyst (infundibular type)

Case of the Week #315:

Various images

Trichilemmal (pilar) type


● 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

Trichilemmal type

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

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