Skin Nonmelanocytic tumors
Adnexal tumors - hair follicles
Pilomatrixoma

Author: Christopher S. Hale, M.D.

Revised: 10 May 2018, last major update June 2012

Copyright: (c) 2002-2018, PathologyOutlines.com, Inc.

PubMed Search: Pilomatrixoma [title] "loattrfree full text"[sb]

Cite this page: Hale, C.S. Pilomatrixoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skintumornonmelanocyticpilomatrixoma.html. Accessed October 17th, 2018.
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:

Contributed by Mark R. Wick, M.D.

Breast skin



Images hosted on other servers:

Various images

Gross description
  • Nodular, subepidermal
Gross images

Images hosted on PathOut server:

Contributed by Mark R. Wick, M.D.

Breast skin

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:


Contributed by Andrey Bychkov, M.D., Ph.D.

Nodule in derma

Basaloid nests

Basal cells, giant cells and ghost cells

Ghost cells



Contributed by
Mark R. Wick, M.D.

Breast skin

 

Contributed by
Dr. Amy Lynn

Pilomatrixoma



Contributed by Dr. Asmaa Gaber Abdou and Dr. Mona Kandil


Various images



Case of the Week #424

Various images



Images hosted on other servers:

Earlobe mass

Evolution of basaloid cells into shadow cells



Images hosted on Flickr:



Contributed by Dr. Ulrich Vogel

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