Incidental anorectal pathologic findings in prostatic needle core biopsies: a 13-year experience from a genitourinary pathology consult service

SummaryFragments of anorectal mucosa are frequently present in transrectal prostate core biopsy specimens. Pathologic findings within the anorectal mucosa are easily overlooked, in part because of their rarity and because anorectal mucosa is not the focus of examination. We reviewed pathologic reports of 96 656 prostate biopsies diagnosed in our consultation service from 1997 to 2010. Anorectal lesions were detected in 30 cases, which were summarized as follows: (1) Neoplasia and polyps (n = 10). A flat rectal adenoma with high-grade dysplasia was identified, for which the patient received hemicolectomy. One patient was found to have a rectal carcinoid tumor. Other neoplastic findings included 1 with low-grade B-cell lymphoma, 3 with hyperplastic polyps, 3 with tubular adenomas, and 1 with anal mucosa with high-grade dysplasia that was found to be a contaminant from another case. (2) Inflammatory changes (n = 20). Acute proctitis was found in 12 patients, including 1 with acute radiation proctitis, 2 with inflammatory bowel disease, and 9 with nonspecific proctitis probably due to bowel preparation. Pulse granulomas and nonnecrotizing granulomas were seen in 5 patients, including 3 with diverticular disease, 1 with history of perirectal fistula, and 1 with unknown etiology. Three patients had miscellaneous findings including muciphage reaction, increased eosinophils, and features of collagenous colitis. In conclusion, it is exceedingly rare to find significant pathology in the rectal fragments associated with prostate needle biopsies. Nevertheless, pathologists should evaluate the rectal mucosa for both neoplastic and inflammatory changes to avoid missing clinically significant anorectal diseases.