Inflammatory myoglandular polyps of the colon and rectum. A clinicopathological study of 32 pedunculated polyps, distinct from other types of polyps.

Hitherto unclassified colorectal polyps were identified in 32 patients (23 men and 9 women; mean age, 53 years). The only symptom, which was observed in less than half the patients, was passage of blood or occult blood. Endoscopic examination revealed solitary pedunculated, red polyps with a smooth surface. These polyps were found in the left colon, especially in the sigmoid. Their characteristic features were inflammatory granulation tissue in the lamina propria mucosae, proliferation of smooth muscle, and hyperplastic glands with occasional cystic dilatation. The etiology of this type of polyp is unknown, but it could involve chronic trauma from the fecal stream and from peristalsis of the bowel. These polyps can be differentiated from juvenile polyps and inflammatory polyps by the presence of abundant smooth-muscle cells in the inflamed lamina propria mucosae. They also can be differentiated from Peutz-Jeghers polyps, which appear as hamartomatous structures with tree-like proliferation of muscularis mucosae covered by colonic mucosa without inflammatory granulation tissue. Their locations and macroscopic appearance distinguish these polyps from mucosal prolapse syndrome and polyps developed after colostomy. In addition, these new polyps differ from inflammatory cap polyps in that they lack a fibrin cap. We propose the name inflammatory myoglandular polyps for these polyps, which are distinct clinicopathologically from other types of colorectal polyps.