AIM: To make a quantitative evaluation by image analysis of oestrogen receptors, progesterone receptors, and androgen receptors in papillary hidradenomas and anogenital sweat glands. METHODS: 20 papillary hidradenomas and the anogenital sweat glands detected in surgical specimens selected from 10 vulvectomies for squamous carcinoma, eight haemorrhoidectomies, and one anal polypectomy, all from female patients, were investigated by the avidinstreptavidin peroxidase testing system. RESULTS: 90% of papillary hidradenomas and almost all the anogenital sweat glands showed immunoreactivity for oestrogen receptor and, more weakly, for progesterone receptor, with immunolabelled nuclear area ranging from 10% to 90%. Conversely conventional sweat glands did not show any nuclear staining. Overexpression of androgen receptors occurred in 20% of papillary hidradenomas, with nuclear staining strictly bordering papillary epithelium with apocrine differentiation. There was no immunoreactivity for androgen receptors in anogenital sweat glands. CONCLUSIONS: Oestrogen and progesterone receptors seem to represent reliable markers for differentiating between anogenital sweat glands and conventional sweat glands, and a further link to explain why papillary hidradenomas occur almost exclusively in the female anogenital region. Positivity for oestrogen/progesterone receptors suggests that epithelia either of anogenital sweat glands or of papillary hidradenomas are controlled by ovarian steroid hormones. Androgen receptor nuclear staining of the epithelium with apocrine differentiation in vulvar papillary hidradenoma strengthens its homology with breast duct papilloma.