An 84-year-old woman with a history of hypertension, venous thromboembolic disease with inferior vena cava filter placement, and anemia was admitted with upper gastrointestinal bleeding. Esophagogastroduodenoscopy revealed an intraluminal mass at the duodenal sweep measuring 8.0 x 5.6 x 4.6 cm and a follow up CT-scan revealed additional tumors in liver and spleen. Related endoscopic images (Figures A & B) and tumor photomicrographs are provided. Which of the following is the most accurate diagnosis of this tumor?

A. Epithelioid hemangioendothelioma 

B. Gastrointestinal stromal tumor (GIST)

C. Malignant GI neuroectodermal tumor

D. Mesothelioma