PILOMATRICOMA

By Gary M. White, MD

pilomatricoma A hard, subcutaneous nodule in an child.


The pilomatricoma (PM) is a calcified tumor which seems to have its origin from the hair matrix cells. It may occur at any age, most commonly between 0 and 20 years of age, but there is another peak in the 50-70 age range.

Clinical

A hard, irregular, dermal or subcutaneous tumor in a child, often on the head or neck, is characteristic. The typical lesion is between 1.0 and 1.5 cm in size. Females are more commonly affected. The overlying skin may be red, bullous, or flesh-colored. The tumor is often rock hard in consistency and an irregular surface may be appreciated. Usually the skin over the lesion is smooth and stretching the skin may show its multifaceted nature--the so called "tent sign." Occasionally, the skin may be keratotic, resembling an SCC or telangiectatic, resembling a BCC. Rarely, the overlying skin may wrinkle, a result of secondary anetoderma. Histologic studies suggest that the anetodermic pilomatricoma seems to arise from mechanical trauma to the overlying skin. If the skin is too thin, it may perforate allowing the extrusion of calcium.

One patient had such anetodermic overlying skin that the lesion was described as a marble in a sac [JEADV 2016;1390].

Differential Diagnosis

A perfectly spherical nodule is more likely to be an epidermal inclusion cyst (EIC). The PM tends to be harder and with "bumpy" edges. Also, the PM is much more common in children whereas the EIC is more common in adults. Rapid growth should prompt a biopsy as rarely, pilomatrix carcinoma may occur.

Syndromes

Pilomatricomas may be multiple and familial or associated with myotonic dystrophy. Pilomatricoma-like changes have occurred in the cysts of Gardner syndrome.

Treatment

Surgical excision is usually required as spontaneous resolution is uncommon. Incision with extraction/curettage is the least intrusive, but often excision is performed. If a child is not bothered by it, surgery may be delayed until the child can tolerate local anesthesia.

One article recommended the following for removal with minimal scarring [PD 2017;34;622]: After the usual prep and cleansing, a 4-mm punch biopsy was performed. Then, all cystic material and cyst wall were curetted from the punch site and 25% trichloroacetic acid (TCA) was applied using a curette and then a cotton-tipped applicator. The wound was left to heal by secondary intention with a pressure dressing placed.

Additional Pictures

This one on the shoulder was inflamed.

pilomatricoma pilomatricoma

Two pilomatricomas after surgical removal--hard and rough calcified nodules.
pilomatricoma, surgical specimens

References

Bullous pilomatricoma. Int J Trichol 2013;5:32-4
Giant pilomatricoma. Journal of the Saudi Society of Dermatology & Dermatologic Surgery (2013) 17, 33–35

Large lesion on the chest. JAAD Case Reports July 2015 Volume 1, Issue 4, Pages 169–171

Anetodermic pilomatricoma. JAAD 2008;58;535–536

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