Intracholecystic papillary neoplasm associated with an invasive carcinoma with cholecystocolonic fistula: a case report.

Intracholecystic papillary neoplasm and cholecystocolonic fistula are both relatively rare diseases. Here, we report a case of a preoperative intracholecystic papillary neoplasm associated with invasive carcinoma and a transverse colonic fistula of the gallbladder. A 79-year-old female patient presented to our hospital with persistent right upper quadrant pain for several months and was suspected to have intracholecystic papillary neoplasm associated with an invasive carcinoma by computed tomography and endoscopic ultrasound. A gallbladder tumor biopsy was pathologically diagnosed as intracholecystic papillary neoplasm. Preoperative cholecystocolonic fistula diagnosis enabled planning not only for cholecystectomy, but also for transverse colon partial resection. Pathological examination of the resected specimen revealed intracholecystic papillary neoplasm associated with an invasive carcinoma with subserosal invasion. No malignant findings were observed in the fistula. This is a rare condition, but the presence or absence of cholecystocolonic fistula should be considered before performing intracholecystic papillary neoplasm surgery.