Skin nonmelanocytic tumor
Adnexal tumors - hair follicles
Proliferating pilar tumor


Topic Completed: 1 June 2012

Revised: 10 April 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Pilar tumor
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Cite this page: Hale CS. Proliferating pilar tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skintumornonmelanocyticpilartumor.html. Accessed April 25th, 2019.
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

Images hosted on other servers:

Pilar tumor

Gross description
  • Pure tumors are multinodular, may be huge
  • May coexist with trichilemmal cyst
Microscopic (histologic) 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
Microscopic (histologic) images

Images hosted on other servers:

Various images

Molecular / cytogenetics description
  • Nondiploid DNA
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