Inflammatory cloacogenic polyp. A unique inflammatory lesion of the anal transitional zone

This report describes the clinical and pathologic features of eight cases of an unusual inflammatory polyp arising from the transitional zone of the anus. This lesion has been designated as the inflammatory cloacogenic polyp. Rectal bleeding is the most common presenting clinical symptom. The polyp is usually located on the anterior wall of the anal canal. Morphologically, it is characterized by a tubulovillous pattern of growth, superficial ulceration, displaced groups of crypts into submucosa, and extension of chronically inflamed fibromuscular stroma into the lamina propria. Clinical and morphologic similarities with the solitary rectal ulcer syndrome suggests that prolapse of transitional zone mucosa may be important in its pathogenesis. Simple surgical resection appears to be the treatment of choice.