Skin nonmelanocytic tumor


Proliferating pilar tumor

Topic Completed: 1 June 2012

Minor changes: 17 January 2022

Copyright: 2002-2022,, Inc.

PubMed Search: Pilar tumor

Christopher S. Hale, M.D.
Page views in 2021: 16,253
Page views in 2022 to date: 917
Cite this page: Hale CS. Proliferating pilar tumor. website. Accessed January 21st, 2022.
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
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:

Trichilemmal type keratinization

Molecular / cytogenetics description
  • Nondiploid DNA
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