A Large Pedunculated Polyp With Surprising Pathology Results

Abstract

We present a unique case of an inverted diverticulum mimicking a large adenomatous pedunculated polyp. Inverted colonic diverticulosis (ICD) is a rare finding described in 0.7% of colonoscopies.1 ICD is typically a few millimeters in size, located in the sigmoid colon and resembles a polyp. Our finding was unusual based on its size, location and appearance. An initial colonoscopy on a 50-year-old male found a pedunculated polyp in the transverse colon with a 2.0 cm stalk and 9 mm polypoid head. Believed to be an adenomatous polyp by inspection with a firm head, snare cautery was used to remove the polyp. The patient tolerated the procedure well without complication. Surprisingly, histology showed polypoid prolapsing mucosa fold consistent with a diverticular disease associated polyp. The differential diagnosis of a pedunculated colonic lesion is broad including an adenomatous pedunculated polyp, a mucosubmucosal elongated polyp, an inflammatory polyp, a filiform polyp associated with inflammatory bowel disease, autoamputation of a pedunculated polyp, ICD and rarely colonic intussusception of an adenoma. There can be significant overlap between inflammatory polyps and prolapse polyps, but the smooth muscle extending between glands is fairly iconic of prolapse polyps and not found in other entities. Our patient's histopathology was consistent with ICD (Figure 1b). Generally, ICD mucosal pattern on a lesion is similar to surrounding mucosa. In our case, the endoscopic appearance of the polyp head was not similar to the stalk one. Hypothetically, this could be due to vascular congestion, trauma of the polyp head, or the presence of inflammatory changes. Histologically, the latter seems to fit best as there is clear crypt architectural abnormalities seen on the head not seen on the stalk or base. ICD may appear polypoid and even present as pedunculated polyps. It is important for endoscopists to distinguish between ICD and adenomatous polyps to prevent complications that can arise with biopsy. In our patient, there was no evidence of perforation likely due to the cautery that sealed the mucosa closed. If there is suspicion of ICD after polyp removal, a resolution clip or over the scope clip could close the defect and prevent complications.Figure: Histopathology of lesion with lobulation and fibrous septa.Figure: focal epithelial denudation, hyperplastic crypt architecture with branching crypts, a lamina propria with prominent fibromuscular proliferation and smooth muscle projections between individual glands, a polymorphic inflammatory infiltrate, dilated capillaries, and hypertrophy and upward extension of the muscularis mucosae.Figure: High definition endoscopic image of transverse pedunculated polyp.