BACKGROUND The incidence of carcinoma found within an internal hemorrhoid specimen is exceptionally rare. Further, the presence of primary anal canal adenocarcinoma within internal hemorrhoids is even more infrequent. We describe a case in which anal canal adenocarcinoma was found within an internal hemorrhoidectomy specimen and perform a review of the current literature. CASE SUMMARY The patient was a 79-year-old male who presented with rectal bleeding and was found to have large thrombosed internal hemorrhoids during screening colonoscopy. The patient subsequently underwent a three-column hemorrhoi-dectomy. Pathologic analysis revealed one of three specimens containing a 1.5 cm moderate-to-poorly differentiated adenocarcinoma of anal origin with superficial submucosal invasion. At three-month follow up, he was taken to the operating theatre for biopsy and re-excision of his non-healing wound, which showed no recurrence. His wound has since healed and he was cancer free at ten-month follow up. CONCLUSION When faced with primary anal canal adenocarcinoma an interdisciplinary approach to treatment should be considered. Routine pathological analysis of hemorrhoidectomy specimens may be beneficial due to the severity of anal canal carcinomas if left undiagnosed and untreated in a timely manner.