Abstract
A 61-year-old man visited a local clinic for abdominal pain and was diagnosed with cholelithiasis. Detailed preoperative examination showed early colon cancer at the hepatic curvature of the transverse colon, but endoscopic resection was considered difficult, so he was referred for surgery. He underwent laparoscopic right hemicolectomy and cholecystectomy. During surgery, a mass was observed in the cystic duct, which was excised so as to include the tumor. The resected specimen showed a yellow, semipedunculated tumor measuring 14×10 mm in the cystic duct. On histopathological examination, tumor cells showed circular-to-oval nuclei and eosinophilic granular reticulum, and grew in alveolar, trabecular, or ribbon-like shapes. Immunostaining showed positive findings for synaptophysin and chromogranin A, and negative results for CD56. Ki-67 index was 3-4%. Cystic duct carcinoid was diagnosed. The tumor did not show any mitotic figures or vascular or perineural invasion, but did show invasion into the fibromuscular layer. As of 4 years and 6 months postoperatively, no recurrences have been encountered.
