A Case of Non-Invasive Intracholecystic Papillary Neoplasm Arising from the Rokitansky-Aschoff Sinus

A 76-year-old woman was referred to our hospital for examination and treatment of a gallbladder tumor, which had been detected in the fundus of the gallbladder by abdominal US. Contrast-enhanced abdominal CT showed an intracystic papillary tumor that was slightly enhanced with a contrast agent, suggesting gallbladder cancer. Laparoscopic whole layer cholecystectomy indicated no malignancy in No.12c lymph nodes by intraoperative frozen section diagnosis. Histopathological findings showed intracholecystic papillary neoplasm (ICPN) in the Rokitansky-Aschoff sinus (RAS). In immunohistochemistry, MUC5AC was diffusely expressed and Hep-par1 was partially expressed in the tumor epithelium, whereas MUC1, MUC2, MUC6, and CDX2 were not expressed. The gallbladder tumor was diagnosed as high-grade ICPN corresponding to the oncocytic subtype. Non-invasive ICPN arising from the RAS is very rare and has a relatively good prognosis after cholecystectomy; however, there is a need for careful follow-up of the patient after surgery.