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Skin - Nonmelanocytic tumors

Adnexal tumors-hair follicles

Pilar tumor


Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 5 July 2012, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Also called proliferating trichilemmal cyst
● Neoplastic version of trichilemmal cyst
● Women > men, base of neck and scalp
● Usually benign, may recur locally, metastases are very rare and seen only with obvious malignant cytologic features resembling a focal trichilemmal carcinoma or a sarcomatoid carcinoma

Case reports
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● 64 year old man with tumor on scalp (Dermatol Online J 2008;14;10:25)

Clinical images
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Pilar tumor

Gross description
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● Pure tumors are multinodular, may be huge
● May coexist with trichilemmal cyst

Micro description
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● Solid with pushing borders and lobulated contour, usually involves epidermis but may open into skin surface
● Bands of squamous epithelium with trichilemmal-type keratinization
● May have prominent atypia, focal stromal invasion

Micro images
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Various images

Molecular
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● Nondiploid DNA

Differential diagnosis
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● Trichilemmal cyst
● Malignant pilar tumor
● Squamous cell carcinoma

End of Skin - Nonmelanocytic tumors > Adnexal tumors-hair follicles > Pilar tumor


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