Abstract
A 47-year-old woman presented to our hospital with an acute abdomen. She had muscular guarding and tenderness throughout her abdomen, and computed tomography (CT) showed massive ascites. Diffuse peritonitis was suspected, and emergency laparotomy was performed. Laparotomy showed no gastrointestinal perforation, but yellow ascitic fluid and white, hard nodules disseminated throughout the abdominal cavity were seen. The laparotomy was only exploratory. Poorly differentiated adenocarcinoma was detected in the nodules and ascitic fluid removed during surgery, and the patient was diagnosed with carcinomatous peritonitis of unknown origin. Based on immunostaining of the peritoneal nodules, the tissue was pathologically diagnosed as being of breast cancer origin. Although no tumors were palpable in either breast, CT showed a faint shadow in the left mammary gland, and core needle biopsy of the site revealed a poorly differentiated adenocarcinoma that was pathologically similar to the peritoneal dissemination. The primary tumor was therefore identified as breast cancer.
