• Lichen sclerosus et atrophicus (LS&A) of the vulva and perianal skin is an atrophic condition that can occur alone or in association with additional lesions situated elsewhere on the skin surface. The cases of three sisters with LS&A of the vulva are reported herein; in one a squamous cell carcinoma developed in a hyperplastic area of mixed dystrophy (LS&A with fociof hyperplasia). Familial occurrences of LS&A are rare. Malignant neoplasms arising in areas of LS&A have been reported previously. Squamous cell carcinoma arises in hyperplastic areas of mixed dystrophy where there is evidence of both LS&A and epithelial hyperplasia. (Arch Dermatol1982;118:329-331)