Eruptive vellus hair cyst. Clinical and histologic findings.

This is, to our knowledge, the second report of eruptive vellus hair cysts. The lesions, which occurred in an 18-year-old woman, consisted of 35 to 40 brownish-black, 1- to 4-mm papules on the anterior aspect of the chest. Histologically, the lesions consisted of small cysts in the middle dermis that contained laminated and amorphous keratinous material and vellus hairs. The cyst wall consisted of several layers of squamous epithelium with a rudimentary follicle attached to its outer aspect. The lesions regressed spontaneously after ten months. The pathogenesis is obscure but the condition appears to be a new distinctive entity.