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- Benign, adnexal skin tumor derived from hair matrix cells
- Slow-growing, hard, typically solitary nodule found in the dermis/subcutaneous layer of the skin
- Most commonly occurs on the head and neck of children and young adults (1)
- Pilomatrix carcinoma, a rare malignant variant, can be locally invasive and have a high recurrence rate. Infrequent cases of metastases have been reported.
- Perforating pilomatricoma
- Synonym(s): pilomatrixoma; calcifying epithelioma of Malherbe; trichomatricoma
- System(s) affected: integumentary
- Pilomatricoma was first described in 1880 by Malherbe and Chenantais (2).
- Incidence of pilomatricomas has not been well studied.
- One study reported an incidence of 1.04% of all benign skin tumors examined and 0.08% of all histologic samples reviewed.
- Slight female preponderance (male-to-female ratio, 1:1.1)
- Most frequently occurs in patients <20 years old (37–46%), with some reports of a second smaller peak in the 5th to 7th decades of life
Etiology and Pathophysiology
- Pilomatricomas derive from the primitive basaloid cells of the epidermis that differentiate into hair matrix cells with uncontrolled proliferation in the dermis/subcutaneous tissue
- There are anecdotal reports of lesions arising in areas of trauma, insect bites, and surgery (3.9% of cases).
- Activating β-catenin gene (CTNNB1) mutations are thought to play an important role.
- A high level of β-catenin results in the stimulation of cellular proliferation and/or inhibition of cell death.
No known risk factors
Commonly Associated Conditions
Although uncommon, multiple pilomatricomas have been associated with the following conditions:
- Myotonic dystrophy
- Turner syndrome
- Rubinstein-Taybi syndrome
- Trisomy 19
- Sotos syndrome
- Gardner syndrome