A 58-year-old man requests removal of a lesion on his left forearm. The growth was noted more than 2 years ago and has enlarged gradually to its present size. He denies similar lesions elsewhere. Examination reveals a 1.2-cm whitish firm cystic nodule with no evidence of a dilated pore. No tenderness is elicited on palpation.
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The lesion was excised and histopathology confirmed a diagnosis of pilomatricoma. Pilomatricomas are benign appendageal cystic lesions with differentiation toward hair cells. They were first described 135 years ago by Malherbe and Chenantais.1
Most pilomatricomas are solitary and asymptomatic, with a normal overlying epidermis. They are more common in children,2,3 but the neoplasms can arise at any age, occurring in adults mainly between age 50 and 66 years.4,5 Transformation to malignancy is rare.
Definitive diagnosis is made by biopsy. Microscopic analysis reveals islands of epithelial cells comprised of 3 distinct subtypes: basophilic cells with scant cytoplasm, shadow cells with a central pallor, and transitional cells between basophilic and shadow cell types.6 Calcium deposits are seen in most pilomatricomas.
Pilomatricomas do not regress spontaneously, and the treatment of choice is surgical excision.7 Resection margins of at least 1 cm is recommended to prevent recurrence.
Stephen Schleicher, MD, is an associate professor of medicine at the Commonwealth Medical College and an adjunct assistant professor of dermatology at the University of Pennsylvania Medical College. He practices dermatology in Hazleton, Pennsylvania.
- Malherbe A, Chenantais J. Note sur l’epithelioma calcifie des glandes sebacees. Prog Med. 1880;8:826-828.
- Wells NJ, Blair GK, Magee JF, Whiteman DM. Pilomatrixoma: a common, benign childhood skin tumour. Can J Surg. 1994;37(6):483-486.
- Demircan M, Balik E. Pilomatricoma in children: a prospective study. Pediatr Dermatol. 1997;14(6):430-432.
- Kaddu S, Soyer HP, Cerroni L, Salmhofer W, Hödl S. Clinical and histopathologic spectrum of pilomatricomas in adults. Int J Dermatol. 1994;33(10):705-708.
- Julian CG, Bowers PW. A clinical review of 209 pilomatricomas. J Am Acad Dermatol. 1998;39(2 Pt 1):191-195.
- Elder D, Elenitsas R, Ragsdale BD. Pilomatricoma. In: Elder D, Elenitsas R, Jaworsky C, Johnson B Jr. Lever’s Histopathology of the Skin. 8th ed. Philadelphia, PA: Lippincott-Williams & Wilkins; 1997:757-759.
- Thomas RW, Perkins JA, Ruegemer JL, Munaretto JA. Surgical excision of pilomatrixoma of the head and neck: a retrospective review of 26 cases. Ear Nose Throat J. 1999;78(8):541, 544-546, 548.