A Tumor Localized in the Portal Vein

Abstract

Question: A 56-year-old man underwent annual abdominal ultrasonography (US) as a medical checkup and a mass was found in his portal vein. Further examination was required and he was admitted to our hospital. He had no significant chief complaints, family history, or past medical history. On physical examination, no significant findings were revealed. Laboratory data were as follows: aspartate aminotransferase of 57 IU/L, alanine aminotransferase of 42 IU/L, lactate dehydrogenase of 302 IU/L, and γ-glutamyltransferase of 248 IU/L. Tumor markers were as follows: carcinoembryonic antigen of 4.7 ng/mL carbohydrate antigen 19-9 of 0.9 U/mL, alpha-fetoprotein of 8.6 U/mL, DUPAN-2 of 155 U/mL, neuron-specific enolase of 17.74 ng/mL, and protein induced by vitamin K absence-2 of 18 mAU/mL. Serologic tests for hepatitis B virus and hepatitis C virus were negative. Abdominal US demonstrated a mass occupying the portal vein near the head of the pancreas (Figure A). Doppler examination demonstrated no blood flow in the portal vein. Early phase-enhanced computed tomography (CT) showed a homogenously enhanced mass occupying the portal vein and it elongated to secondary branches of the right intrahepatic portal vein and the superior mesenteric vein (Figure B). On CT and endoscopic US (EUS) examinations, there were no other detectable lesions suggesting primary tumors in the pancreas, liver or other organs. Positron emission tomography (PET) CT disclosed high enhancement in portal vein identical to the mass lesion (Figure C). How do you diagnose the tumor? What is the most likely diagnosis? See the Gastroenterology web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI. To make a histologic diagnosis, we performed endoscopic ultrasound fine needle aspiration (Figure D). Microscopically, the tumor showed an alveolar growth pattern and cells were eosinophilic and some of them were amphophilic (Figure E). Immunohistochemical staining for both bcl-10 (Figure F) and trypsin (Figure G) was positive in the tumor. These microscopic features were consistent with acinar cell carcinoma of the pancreas. Because the tumor was invaded into secondary branches of both the right and left intrahepatic veins and the superior mesenteric vein, the tumor was considered to be unresectable. We started treating the tumor with chemotherapy. Acinar cell carcinoma is a rare malignant epithelial neoplasm and represents 1% to 2% of all exocrine pancreatic neoplasms.1Sun Y. Wasserman P.G. Acinar cell carcinoma arising in the stomach: a case report with literature review.Hum Pathol. 2004; 35: 263-265Crossref PubMed Scopus (41) Google Scholar We herein described an extremely rare case of pancreatic acinar cell carcinoma localized in the portal vein without any detectable primary lesions in the pancreas or other organs. In our patient, all the imaging studies including US, CT, PET-CT, and EUS could not detect any tumors in the pancreas. There are few case reports on pancreatic acinar cell carcinoma arising from non-pancreatic tissues, including the stomach,1Sun Y. Wasserman P.G. Acinar cell carcinoma arising in the stomach: a case report with literature review.Hum Pathol. 2004; 35: 263-265Crossref PubMed Scopus (41) Google Scholar the ampulla of Vater,2Kawakami H. Kuwatani M. Onodera M. et al.Primary acinar cell carcinoma of the ampulla of Vater.J Gastroenterol. 2007; 42: 694-697Crossref PubMed Scopus (10) Google Scholar and the jejunum.3Makhlouf H.R. Almeida J.L. Sobin L.H. Carcinoma in jejunal pancreatic heterotopia.Arch Pathol Lab Med. 1999; 123: 707-711Crossref PubMed Google Scholar In these cases, tumors were considered to arise from ectopic pancreatic tissue, because these tissues are derived from endoderm. However, in our patient, it is developmentally unlikely that acinar cell carcinoma arise from ectopic pancreatic tissue in the portal vein that is derived from mesoderm. Intraductal growth into the portal vein is also a rare feature for pancreatic acinar cell carcinoma. A few cases with portal tumor thrombus of acinar cell carcinoma have been reported. However, all of these cases had primary lesions in the pancreas and the tumor invaded directly to the portal vein. In conclusion, even though extremely rare, pancreatic acinar cell carcinoma should be included in the differential diagnosis of a tumor localized in the portal vein.