Question:

A 16 year-old girl complained of an asymptomatic warty plaque on the left side of her neck. It was present at birth and had gradually increased in size and thickness. Otherwise she enjoyed good health and had no other similar lesion elsewhere.

Answer: B. Epidermal naevus

This girl had an epidermal naevus. Epidermal naevus is a benign neoplasm usually presenting at birth or shortly after birth. Linear epidermal naevus is a common form, and it is a verrucous hyperplasia of epidermal cells. Usually it is unilateral in distribution and frequently follows Blaschko's lines. The colour may vary from tan to dark brown. Histologically, hyperkeratosis, papillomatosis and sometimes epidermolytic hyperkeratosis can be found. Malignant change in epidermal naevus is rare.

Surgical treatment with excision, cryotherapy, laser or dermabrasion can produce acceptable cosmetic results. The lesion may sometimes recur.