61. Clear cell variant of adenocarcinoma in the periampullary region

Abstract

A tumour involving the periampullary region may have origin in the pancreas, common bile duct, duodenum or ampulla of Vater. Clear cell carcinoma is a common variant of tumours of the kidney, lung, thyroid and female genital tract but is uncommonly described in the pancreas, biliary tract and ampulla. Clear cell carcinoma of the duodenum has not been described. We present a case of 55 year old man who was admitted for gastric outlet obstruction. CT examination demonstrated a pancreatic mass involving the pancreatic head and uncinate process. A periampullary lesion with associated duodenal stricture was seen at endoscopy, biopsy of which showed an infiltrating adenocarcinoma deep to the mucosa, composed of cells with clear cytoplasm containing mucin. The cells were arranged in nests and glands and demonstrated positive CK7 and Ca19.9 staining. A diagnosis of adenocarcinoma suggestive of biliary or pancreatic origin was given. The Whipples procedure was abandoned after intraoperative frozen section revealed liver metastases. Paraffin sections confirmed the liver nodule to have similar morphology and staining characteristics to the periampullary biopsy. PAX8 was negative, ruling out metastatic clear cell renal cell carcinoma. Mutational analysis of tumour cells showed a KRAS G12D mutation, a mutation found commonly in pancreatic, ampullary, and biliary adenocarcinomas. The patient is currently undergoing chemotherapy. The WHO (2010) and AFIP have described clear cell change in pancreatic adenocarcinoma and a clear cell variant of extrahepatic biliary duct and ampullary adenocarcinomas. Other case reports and case series have described clear cell carcinoma of the pancreas and advocate including this as a distinct variant in the pancreatic adenocarcinoma classification. The rarity of these tumours may result in misdiagnosis particularly when presented with a small biopsy. We discuss and briefly review the literature surrounding these entities.