[Uterus in a male: persistent Mullerian duct syndrome. Report of a case with embryological considerations].

We describe a case of persistent mullerian duct syndrome incidentally found in a 79-year-old man. It was characterized by the presence of a uterus-like retroperitoneal mass composed of an ovoidal corpus and rudimental portio with a central lumen. Histologically the mass was leiomyomatous in nature, closely resembling myometrium, while the central lumen was lined by a monolayer of ciliated cuboidal to columnar epithelium similar to embryo-fetal celomatic epithelium. Although this is a dysembryogenetic syndrome due to the lack of regression of the mullerian duct, it may be incidentally discovered in elderly patients, as in the present case during hernioplastic surgery. We also briefly discuss the regression of mullerian duct, focusing on morphological features observed in a large collection of human embryos and fetuses, in order to better understand the pathogenesis of a "uterus' in a male without evidence of sexual abnormalities.