Question: A 45-year-old male patient with a metallic aortic valve prosthesis due to coronary sinus dissection underwent follow-up endoscopies and colonoscopies for refractory iron deficiency anemia. Enterotomography showed a suspected vascular malformation in the proximal jejunum, 10 cm after the Treitz angle. On jejunoscopy, the malformation was represented by a flat, reddish vascular lesion, with neovessels on the surface, measuring 20 mm and occupying about a third of the circumference of this segment (Fig. A). A metallic clip was placed to perform arteriography, which revealed active bleeding; successful embolization was performed (Fig. B). One year later, the patient presented again with iron deficiency anemia. On enterotomography a hypervascular nodular lesion was identified in the same topography as before, with a large feeding vessel (first jejunal branch) measuring 19 × 15 mm; this was confirmed at jejunoscopy by a polypoid lesion, with a reddish surface and covered by fibrin. Its base could not be evaluated (Fig. C). The patient underwent enterectomy, and histology revealed an intense endothelial proliferative process in a slightly lobular pattern (Fig. D). Written informed consent was obtained. Based on the above information, what is the most likely diagnosis?