Fibroepithelial polyp is basically fancy for skin tag and when they're found in the rectum, they're sometimes referred to as hypertrophied anal papillae which is coded to 569.49.
Whether or not you'd use 569.49 or 569.0 is up for debate. I can argue it both ways in my head all by my lonesome, but I definitely wouldn't use 211.4 since adenomas are glandular tumors, not epithelial tumors. The pathology will state whether or not the polyp is an adenoma. If it's reported as any other kind of polyp, then I don't use the 211.4 code.
This is an excerpt from one of my favoritest books: Surgical Pathology of the GI Tract, Liver, Biliary Tract and Pancreas:
Hypertrophied anal papillae, also known as anal fibroepithelial polyps, are benign polypoid projections of anal squamous epithelium and subepithelial connective tissue. They result from enlargement of anal papillae, which are barely perceptible triangular protrusions located at the base of the anal columns (columns of Morgagni). They are present in 45% of patients who undergo proctoscopic examination and are believed to be acquired structures.[21] They are twice as common in men as in women, and range in size from 0.3 to 1.9 mm, with a mean diameter of approximately 1 cm. They may be asymptomatic, in which case they are usually found in isolation as a solitary firm, palpable mass on digital examination, or develop in association with an irritation, infection, or chronic fistula or fissure in the anal canal.[21–23]They may also coexist with hemorrhoids and, not surprisingly, are confused with hemorrhoids …