RESUMO
When a woman presents with an acute abdomen with cystic lesions in the abdominal cavity, the differential diagnosis includes torsion or rupture of an ovarian tumor. We report our experience with a 54-year-old nulliparous woman who underwent emergency surgery for a suspected ruptured ovarian tumor. Intraoperative examination revealed disruption of a cystic tumor that had developed externally from the fundus of the uterus. The patient, who was taking aspirin because of a history of medullary infarction, reported lower abdominal discomfort for several days. When she sought care, she was referred to the gynecology department where transvaginal ultrasonography and contrast-enhanced computed tomography showed a poorly toned mass with a maximum diameter of 20 cm posterior to the uterus. She also had a large amount of ascites reaching around the liver and the spleen. She underwent an emergency laparotomy for a presumed diagnosis of acute abdomen caused by a ruptured ovarian tumor with intra-abdominal bleeding. Intraoperative examination revealed normal adnexae bilaterally, but there was a cystic tumor in the pouch of Douglas that was strongly adherent to the surrounding intestines. This mass was connected to the posterior uterus by a stalk and appeared to be continuous with the uterine tissue. The postoperative pathological diagnosis was carcinosarcoma derived from subserous cystic adenomyosis. This is the first case report of carcinosarcoma developing from subserous cystic adenomyosis in the English literature as far as we know.