Skin - Nonmelanocytic tumors
Adnexal tumors - hair follicles
Pilar tumor

Author: Christopher Hale, M.D. (see Authors page)

Revised: 6 October 2016, last major update June 2012

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Pilar tumor

Cite this page: Pilar tumor. website. Accessed March 29th, 2017.
Definition / General
  • 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
Clinical Images

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Pilar tumor

Gross Description
  • Pure tumors are multinodular, may be huge
  • May coexist with trichilemmal cyst
Micro Description
  • 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 / Cytogenetics Description
  • Nondiploid DNA