42 year old man with acute onset of intestinal obstruction, presenting with vomiting, colic and abdominal distension.
The large bowel shows several sessile and pedunculated cauliflower-like polyps. A portion of the bowel (intussusceptum) has telescoped into the immediately adjacent distal segment (intussuscipien). A polyp is found at the leading edge of the invaginated portion, which propelled by peristalsis, has pulled the mesentery along leading to bowel obstruction, mesenteric lymphovascular compression, and infarction. Note the dusky discoloration of incarcerated portions.
The microscopy pictures show a tubular adenoma, which is the likely mechanical cause of the intussusception.