Polypoid arteriovenous malformation of colon mimicking inflammatory fibroid polyp.

Arteriovenous malformation is a well-known cause of lower gastrointestinal bleeding in the elderly and usually appears as flat or elevated bright red lesions endoscopically. Here we present a 59-year-old woman with a large fungating polypoid mass in the transverse colon. Histologically, the larger vessels were located mainly in the submucosa, and smaller vessels were also observed within the mucosa. Verhoeff's elastic stain showed internal and external elastic lamina in the malformed vessels. We report an extremely rare case of a large, pedunculated, polypoid arterioveneous malformation with the first description of our complete pathological findings.