Abstract:

Introduction: Pilomatricoma is a benign cutaneous adnexal tumor usually located in the deep dermis or subcutaneous fat. The tumor shows hair matrical differentiation characterized by well-defined lobules of matrical cells that transform into ghost cells. Herein we describe a case of pilomatricoma with intraepidermal growth and cutaneous horn formation. Case Report: A 14-year-old girl came to dermatology OPD with a single skin-colored pedunculated growth over the left arm. Dermatological examination revealed skin-colored to yellow-colored thickened growth with underlying induration. The lesion was excised with a clinical diagnosis of cutaneous horn with associated appendigeal tumor. Microscopic examination revealed a markedly thick column of stratum corneum, along with parakeratosis and crusting. The superficial part of the epidermis is replaced by small basaloid cells, which at places are showing abrupt keratinization into ghost-like cells. The morphological features suggest a diagnosis of pilomatricomal horn. Discussion: Cutaneous horns are an uncommon condition and can be associated with a number of disease entities ranging from common entities, including viral warts and seborrheic keratosis to premalignant conditions (solar keratosis) and malignancy (squamous cell carcinoma). The present case, supposed to represent a superficial variant of pilomatricoma, can be confused with in-situ squamous cell carcinoma, basal cell carcinoma, actinic keratosis, or sebaceous carcinoma. Several possibilities for the origin of superficial pilomatricomas are postulated, including undifferentiated stem cells from a superficial portion of the hair follicle or epidermis, or matrical cells of ectopic hair bulbs situated near the epidermis. Since pilomatricomas are deeply located adnexal tumors and the cutaneous horn formation is rare, dermatopathologists should be familiar with this variant.

Financial Disclosure:
No current or relevant financial relationships exist.

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VIKARN VISHWAJEET, MD, DM