Table of ContentsDefinition / general | Case reports | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Differential diagnosis
Cite this page: Hale C. Pilomatrixoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticpilomatrixoma.html. Accessed December 3rd, 2021.
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
- Nodular, subepidermal
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.
Contributed by Mark R. Wick, M.D. and Amy Lynn, M.D.
Contributed by Asmaa Gaber Abdou, M.D. and Mona Kandil, M.D.
Contributed by Ulrich Vogel, M.D.
Images hosted on other servers:
- 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)