Primary Intrahepatic Squamous Cell Carcinoma with Histological Collision of Adenocarcinoma and Squamous Cell Carcinoma: A Case Report

BACKGROUND Cholangiocarcinoma is a rare, aggressive biliary tract malignancy. On histopathology, most tumors are adenocarcinomas, while squamous cell carcinoma of the biliary tract is extremely rare. CASE REPORT An 82-year-old male was admitted due to the detection of a space-occupying lesion at S6 of the liver. On abdominal dynamic computed tomography, there was an irregular mass with inhomogeneous density associated with mild delayed enhancement in the tumor's peripheral zone, measuring approximately 22×25 mm, at S6, with secondary dilated biliary ducts of B6. Endoscopic retrograde cholangiopancreatography showed a severe stricture at B6. Brush cytology of B6 was positive for both adenocarcinoma and squamous cell carcinoma. Furthermore, mucous brushing cytology of the papilla of Vater was also positive for adenocarcinoma. Finally, the preoperative diagnosis of primary intrahepatic cholangiocarcinoma, combined with a cancer of the papilla of Vater, was made. The patient underwent both extended right lobectomy and pancreaticoduodenectomy. Histological examination showed that the majority (>99%) of this liver tumor was composed of keratinizing squamous cell carcinoma. CONCLUSIONS Squamous cell carcinoma of the biliary tree is very rare, since the majority of biliary tree tumors are adenocarcinomas. Cholangiocarcinoma containing a squamous cell component has a poor prognosis. To the best of our knowledge, this is the first case report of a primary intrahepatic squamous cell carcinoma that presented as a solid tumor showing clear histological collision between adenocarcinoma and squamous cell carcinoma and was successfully treated with hepatic resection and achieved disease-free survival of more than one year.