Metastatic Melanoma to the Pancreas Forming Portal Vein Tumor Thrombosis: A Case Report

Abstract

Pancreatic metastasis of malignant melanoma is rare and porto-splenic tumor thrombus associated with malignant melanoma is even less frequent. We report a case of metastatic malignant melanoma involving the pancreas, portal vein, splenic vein and superior mesenteric vein. A 60-year-old man showed an elevated amylase level. He had a history of sigmoid colon adenocarcinoma and malignant melanoma. Computed tomography (CT) and magnetic resonance imaging (MRI) showed extensive thrombosis involving the intra-and extrahepatic portal veins extending into the superior/inferior mesenteric vein and splenic vein. On T1 weighted images, tumor thrombi demonstrated diffusely high signal intensity, which is a characteristic finding in malignant melanoma. Also, thrombus showed prominent diffusion restriction on diffusion weighted images and intense uptake of 18F-fluorodeoxyglucose (18F-FDG) on positron emission tomography (PET). Ultrasound-guided biopsy confirmed the metastatic, malignant melanoma involving the pancreas and the veins. We report an unusual manifestation of metastatic, malignant melanoma to the pancreas with extensive tumor thrombi. Specific MR features including high signal intensity on T1 weighted images and diffusion restriction on diffusion weighted images were helpful in reaching a conclusion.