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Skin - Nonmelanocytic tumors

Adnexal tumors-hair follicles

Pilomatrixoma

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 5 July 2012, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● 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 – 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
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● 9 and 10 year old girls with lesions of earlobe and upper back (Indian J Dermatol 2010;55:390)

Clinical images
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Various images

Gross description
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● Nodular, subepidermal

Micro description
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● 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

Micro images
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Left: contributed by Dr. Amy Lynn, Toledo, Ohio; middle: earlobe mass; right: evolution of basaloid cells into shadow cells

           

               
Contributed by Dr. Asmaa Gaber Abdou and Dr. Mona Kandil, Menofiya University, Egypt

Cytology description
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● 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
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Fine needle aspiration (various images)

Differential diagnosis
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● Basal cell carcinoma

End of Skin - Nonmelanocytic tumors > Adnexal tumors-hair follicles > Pilomatrixoma

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