Skin nonmelanocytic tumor
Adnexal tumors
Hair follicles
Pilomatrixoma
Author: Christopher S. Hale, M.D.
Last author update: 1 June 2012
Last staff update: 31 March 2023 (update in progress)
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Pilomatrixoma [title] "loattrfree full text"[sb]
Table of Contents
Definition / general | Case reports | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Differential diagnosisCite this page: Hale C. Pilomatrixoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticpilomatrixoma.html. Accessed April 1st, 2023.
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
- 9 and 10 year old girls with pilomatricoma (Indian J Dermatol 2010;55:390)
- 34 year old man with an occipital nodule (Case of the Week #424)
Clinical images
Contributed by Mark R. Wick, M.D.
Breast skin
Images hosted on other servers:
Preoperative appearance of face pilomatricoma
Calcified pilomatricoma
Gross description
- Nodular, subepidermal
Gross images
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
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. and Amy Lynn, M.D.
Breast skin
Pilomatrixoma
Contributed by Asmaa Gaber Abdou, M.D. and Mona Kandil, M.D.
Various images
Case #424
Various images
Contributed by Ulrich Vogel, M.D.
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
Case #424
Images hosted on other servers:
H&E, cluster of shadow cells
MGG, cluster of basaloid cells
MGG, abundant cytoplasm
Differential diagnosis
