Anatomical and histological studies of so-called Müllerian duct cyst.

BACKGROUND: We examined so-called Müllerian duct cysts both histologically and immunohistochemically with anatomical observation to investigate the etiology of the 'Müllerian duct cyst'.

METHODS: Five cystic lesions located in the prostatic midline were obtained from surgical specimens. A communication between the cystic lesion and the urethra via the utricular orifice was looked for and the specimens were subjected to histological and immunohistochemical testing.

RESULTS: A communication between the cyst and the urethra was confirmed in four cases, but not in one case. Histological and immunohistochemical examinations of the epithelium lining indicated that its characteristics were identical to those of the prostatic utricle in all cases.

CONCLUSIONS: The so-called Müllerian duct cyst exhibits features comparable to those previously described in the prostatic utricle. There is no evidence that these cystic lesions originate from the Müllerian duct remnant, at least in the epithelial lining. We suggest that they should be termed a prostatic utricular cyst or cystic dilation of the prostatic utricle, depending on whether an outlet to the urethra is absent or present, respectively.