[Diagnosis of Serous Adenocarcinoma following Pneumatosis Intestinalis Development during Bevacizumab Therapy for Cancer of Unknown Primary-A Case Report].

A 75-year-old woman was treated with TC plus Bev for cancer of unknown primary. During treatment, she presented to the clinic with chief complaints of general malaise and anorexia. On presentation, abdominal distention and upper abdominal tenderness were noted, and sepsis was suspected. A thoracoabdominal CT scan revealed prominent intramural emphysema and mesenteric gas in the ascending colon. An emergency laparotomy was performed for suspected pneumatosis intestinalis non-obstructive intestinal ischemia. However, no intra-abdominal contamination or ischemic changes were observed intraoperatively. Histological examination revealed a small adenocarcinoma on the serous surface of the ascending colon, and immunochemical staining confirmed the diagnosis of serous adenocarcinoma as the patient's primary cancer. This report describes a case in which the patient achieved long-term survival after diagnosis. It also emphasizes the importance of identifying the subset of patients with cancer of unknown primary who have a good prognosis in order to provide appropriate treatment.