Last revised by Rohit Sharma on 20 Aug 2023

A pilomatricoma is an uncommon, benign neoplasm thought to arise from hair cortex cells.

It was formerly referred to as pilomatrixoma or calcifying epithelioma of Malherbe.

  • the reported incidence of pilomatricoma ranges between 1 in 500-2000

  • they make up 0.12% of cutaneous neoplasms and 20% of all hair follicle related tumors

  • more common in females; F:M ratio = 3:2

  • more common in the Caucasian population

  • more common in children, but occurrence in adults is increasingly being recognized

  • bimodal peak during the first and sixth decades of life

  • usually develops within the first two decades of life with 40% of cases occurring before the age of 10 years and 60% before the age of 20 years

  • usually solitary but up to 3% are multiple

Recognized associations include:

Familial forms may be present.

The main clinical features of pilomatricoma are:

  • painless

  • slow-growing

  • superficial

  • mobile

  • hard mass

  • ranges in size from 0.5 to 5 cm in diameter

  • overlying skin has a bluish-red discolouration

Approximately 50% of pilomatricoma cases occur in the head and neck region. This is followed by the upper extremities, trunk and the lower extremities. Less commonly seen in the frontal, temporal, cheek, periorbital and preauricular areas.

A pilomatricoma is usually a well-circumscribed nodulocystic tan-colored mass containing irregularly shaped, lobulated islands of cells separated by fine, fibrovascular connective tissue stroma.

Microscopically pilomatricoma​ demonstrates:

  • peripheral basaloid cells, which are darkly stained, round or elongated, with indistinct cell borders and minimal cytoplasm; they contain round to ovoid deeply basophilic nuclei with most showing prominent nucleoli

  • central ghost cells with abundant, pale, eosinophilic cytoplasm and well-defined cell borders and a central clear area

Pilomatrix carcinoma = malignant pilomatricoma (rare)

  • pilomatricomas may show non-specific soft tissue calcification

Pilomatricomas may be seen as

  • ovoid complex mass, often with calcification, at the junction of the dermis and subcutaneous fat with focal thinning of the overlying dermis

  • appear as target lesions with a hypoechoic connective tissue capsule and central hyperechoic epithelial cells

  • pilomatricomas tend to be well-defined, subcutaneous tumors with microcalcifications

  • T1: uniform, homogeneously low to intermediate to high signal

  • T2: variable appearance either inhomogeneous with multiple areas of intermediate signal or homogeneous with either intermediate signal intensity or high signal radiating from the center

  • T1 C+ (Gd): variable post-contrast T1 appearance, where some only enhance peripherally

Surgical resection is often curative for pilomatricomas.

A pilomatricoma was first described by Malherbe and Chenantias in 1880, as a subcutaneous tumor, and was shown to be a derivative from hair cortex cells in 1942 by Turhan and Krainer

The root of the term pilomatricoma is derived from the Latin word 'pilus' meaning hair.

General imaging differential considerations of a pilomatricoma include:

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