Skin - Nonmelanocytic tumors
Adnexal tumors - hair follicles
Pilomatrixoma

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

Revised: 17 May 2017, last major update June 2012

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Pilomatrixoma [title]

Cite this page: Pilomatrixoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skintumornonmelanocyticpilomatrixoma.html. Accessed September 22nd, 2017.
Definition / general
  • Also called pilomatricoma, calcified epithelioma of Malherbe
  • Benign tumor arising from hair matrix
  • Usually children and young adults in head, neck or upper extremities
  • Proliferating portion of tumor composed of small round blue cells - a pitfall on fine needle aspiration

  • Aggressive pilomatrixoma:
    • Atypical histology, locally invasive with local recurrence
  • Malignant pilomatrixoma:
    • Cytologic atypia, infiltrative border, transition to squamous cells
    • Clear cells, necrosis, mitotic figures, variable sarcomatoid features
    • Recurs locally, may metastasize
Case reports
Clinical images

Images hosted on PathOut server:

Breast skin, courtesy of Mark R. Wick, M.D.



Images hosted on other servers:

Various images

Gross description
  • Nodular, subepidermal
Gross images

Images hosted on PathOut server:

Breast skin, courtesy of Mark R. Wick, M.D.

Microscopic (histologic) description
  • Solid nests of basaloid cells undergoing abrupt trichilemmal-type keratinization
  • Ghost cells, often foreign body reaction, calcification or ossification with extramedullary hematopoiesis
  • Occasional transepidermal perforation
Microscopic (histologic) images

Images hosted on PathOut server:

Breast skin, courtesy of Mark R. Wick, M.D.

Courtesy of Dr. Amy Lynn





Courtesy of Dr. Asmaa Gaber Abdou and Dr. Mona Kandil



COW #424, courtesy of Dr. R. F. Chinoy, Prince Aly Khan Hospital, Mumbai (India)



Images hosted on Flickr:



Courtesy of Dr. Ulrich Vogel



Images hosted on other servers:

Earlobe mass

Evolution of basaloid cells into shadow cells

Cytology description
  • Ghost cells, groups of basaloid cells, squamous cells in combination with multinucleated giant cells and calcium deposits in a background of debris (J Cytol 2011;28:1)
Cytology images

Images hosted on PathOut server:

COW #424, courtesy of Dr. R. F. Chinoy, Prince Aly Khan Hospital, Mumbai (India)

COW #424, courtesy of Dr. R. F. Chinoy, Prince Aly Khan Hospital, Mumbai (India)



Images hosted on other servers:

H&E, cluster of shadow cells

MGG, cluster of basaloid cells

MGG, abundant cytoplasm

Differential diagnosis