[Proliferating serous papillary cystadenoma of the borderline type in myometrium of the fundus uteri].

The 68-year old patient with clinical signs of peritonitis was laparotomized, and a cystic, ruptured structure thought to be an endometriotic cyst was found intraoperatively in the fundus uteri. Histomorphological investigation, however, revealed a proliferating serous papillary cyst-adenoma (borderline tumour) of the myometrium with surrounding, partially atypical endosalpingiosis.