Rectal implantation cysts can occur at anastomotic sites after low anterior resection (LAR) for rectal cancer. Herein, we report a case of primary adenocarcinoma arising from a rectal implantation cyst after LAR for rectal cancer. A 70-year-old woman was referred to our hospital for diagnosis and treatment of a growing cystic lesion. She had LAR performed for rectal cancer 29 years previously and had a rectal implantation cyst detected 13 years previously. On the first visit to our hospital, serum CEA and CA19-9 levels were elevated, and computed tomography (CT) scans revealed a cystic lesion near the anastomosis. CT-guided biopsy revealed no cancer tissue in the cystic lesion. After that, the cystic lesion naturally shrank, and serum CEA and CA19-9 levels became normal. Follow-up included 3 monthly serum CEA and CA19-9 testing and 6 monthly CT scans. Two years later, serum CEA and CA19-9 levels were elevated again. Colonoscopy revealed an ulcerative lesion at the anastomotic site, in which adenocarcinoma was confirmed. Abdominoperineal resection with sacral resection was performed, and postoperative histopathological examination revealed a primary adenocarcinoma with mucinous component at the implantation cyst. Since rectal implantation cysts can become malignant after extended periods, clinicians need to be aware of this disease.
Keywords: Adenocarcinoma; Implantation cyst; Low anterior resection; Rectal cancer.
© 2024. Japanese Society of Gastroenterology.