Skin nonmelanocytic tumor

• Pilomatricoma is a benign skin adnexal tumor originating from hair matrix and cortex

• Benign skin adnexal tumor originating from hair matrix and cortex
• Most commonly occurs in head and neck, extremities and trunk in children
• Grossly appears as circumscribed hard dermal tumor with cheesy material
• Most cases behave indolently without recurrences

• Pilomatrixoma
• Calcifying epithelioma of Malherbe (not recommended)

• ICD-O: 8110/0 - pilomatrixoma, NOS
• ICD-11: 2F22 & XH9E37 - benign neoplasms of epidermal appendages & pilomatricoma, NOS

• Pilomatricoma, being the most common adnexal neoplasm in children, favors young age (Actas Dermosifiliogr 2010;101:771)
  • However, a wide age range has been described from 3 months to 93 years
• Females are affected slightly more than males
• Usually solitary but multiple lesions can occur (Int J Dermatol 2017;56:1032)

• Head and neck are the most common sites of involvement, followed by upper and lower extremities and then trunk
• Ear (J Pediatr 2011;158:511, Ear Nose Throat J 2013;92:34)
• Eyelid (Int J Trichology 2011;3:31)
• Digits
• Male breast (Breast J 2019;25:1012)

Contributed by Nasir Ud Din, M.B.B.S.


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Contributed by Mark R. Wick, M.D.


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Contributed by Mark R. Wick, M.D.


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Contributed by Nasir Ud Din, M.B.B.S. and Andrey Bychkov, M.D., Ph.D.

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Contributed by R. F. Chinoy, M.D. (Case #424)


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A 5 year old girl presented with a hard nodule on her arm. Fine needle aspiration yielded clusters of epithelial cells with scant cytoplasm, some anucleated and nucleated squamous cells. Focal calcified debris was noticed. Which immunohistochemical stain is helpful in diagnosis?

1. Beta catenin
2. CK5/6
3. Ki67
4. p40
5. p53

A. Beta catenin. Beta catenin is the defining molecular alteration in pilomatricoma and nuclear staining of basaloid cells is diagnostic. Answers B and D are incorrect because CK5/6 and p40 expression is also seen in squamous cell carcinoma and some basal cell carcinoma. Answer E is incorrect because p53 aberrant expression is significant for malignant behavior and does not help in the identification of pilomatixoma. Answer C is incorrect because Ki67 will show increased staining in basaloid cells and other inflammatory cells (if present in the adjacent stroma). Identification of abrupt keratinization and ghost cells is based on H&E section.

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Reference: Pilomatrixoma

A 20 year old man had multiple gradually enlarging, itchy scalp tumors for the past 2 years. On examination it was hard nodule and overlying skin was stretched, revealing multiple facets and angles resembling a tent. The excision specimen revealed features as shown in the photomicrograph above. The patient's history is significant for total colectomy a year ago with more than 100 polyps. What is the patient suffering from?

1. Gardner syndrome
2. Gliomatosis cerebri
3. Myotonic dystrophy
4. Rubinstein-Taybi syndrome
5. Turner syndrome

A. Gardner syndrome. The photomicrograph shows a classic picture of basaloid cells and shadow cells, consistent with pilomatricoma. Multiple lesions and past history of total colectomy with more than 100 polyps favors familial adenomatous polyposis related syndrome, specifically Gardener syndrome. Multiple pilomatricoma (6 or more) are significant for association with various syndromes, most involving myotonic dystrophy and familial adenomatous polyposis related syndromes (including Gardner syndrome). Other syndromes include Turner syndrome, Rubinstein-Taybi syndrome, Sotos syndrome (relatively scant) and Kabuki syndrome.

Answer C is incorrect because myotonic dystrophy is part of a group of autosomal dominant disorders with high penetrance that show skeletal and respiratory muscle weakness and myotonia. Other findings may be cardiac muscle abnormalities and conduction defects, cataracts, daytime somnolence and endocrine disorders.

Answer E is incorrect because in Turner syndrome, patients are female and lack part or all of the second sex chromosome. Characteristic features include short stature, premature ovarian failure and high risk for various phenotypic abnormalities (e.g., high palate, nail dysplasia, low posterior hairline, widely spaced nipples, webbed neck and low set or malrotated ears), as well as other medical problems such as cardiovascular defects, skeletal anomalies and autoimmune disorders. It is suggested that growth hormone (or its effector molecule insulin-like growth factor 1) and estrogen may promote hair follicle growth and inhibit apoptosis, as well as produce pilomatricomas.

Answer D is incorrect because Rubinstein-Taybi syndrome is a rare genetic disorder characterized by mental retardation and multiple congenital anomalies. It involves broad thumbs and toes, short stature, distinctive facial features and varying degrees of intellectual disability. Low set ears, cataracts, microcephaly and cryptorchidism may also be seen.

Answer B is incorrect because gliomatosis cerebri is a diffuse growth pattern of glioma that invade multiple lobes of the brain. By definition, more than 2 brain regions have to be affected and symptoms include epilepsy, headaches and behavioral changes.

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Reference: Pilomatrixoma