A 13-year-old girl presents to your clinic with new-onset hematochezia for 1 week. She is currently passing two soft, formed stools per day, each with blood mixed throughout the stool substance. Her history is otherwise unremarkable. Her family history is remarkable for fatal colon cancer in her paternal grandfather at 38 years, colon cancer in her father at age 26 years (treated with chemotherapy and colectomy), and colon cancer in her 19-year-old brother, who is currently undergoing chemotherapy after colectomy. Her exam is normal, without evidence of tachycardia or other signs of significant anemia.
You recommend colonoscopy to better define the source of bleeding and find the following endoscopically: