Vegetating Lesions that Appear in the Scar after Neoadjuvant Therapy for Rectal Tumors: Tumor Regrowth or Benign Neoplasm?

Introduction After the diagnosis of neoplasm of the middle and distal rectum, patients are often submitted to oncological treatment by neoadjuvant therapy. At the end of this treatment, those patients who show complete clinical response can choose, together with their physician, to adopt the watch-and-wait strategy; although it implies lower morbidity for the patient, this strategy is dependent on strict adherence to treatment follow-up for the early identification of any future local injury. Materials and Methods Survey of data from medical records and description, and discussion of case reports with a literature review in books and databases. Results We report the case of a 73-year-old patient diagnosed with moderately differentiated adenocarcinoma of the middle rectum, Stage II (cT3bN0M0), who presented complete clinical response after undergoing treatment with neoadjuvant therapy.Together with the assistant team, the watch-and-wait strategy was chosen. During the follow-up, an endoscopic examination showed a vegetating at the proximal limit of the tumor scar. We chose to perform submucosal endoscopic dissection. The report of the anatomopathological examination evidenced a serrated adenoma with narrow margins free of neoplasia. Conclusion Patient adherence to cancer treatment using the watch-and-wait strategy is essential for the early identification of new local lesions. After resection of the lesion identified in the tumor scar site as a neoplasm-free lesion, it is consistent to think that this lesion would be the origin of the neoplasm, given the adenomatous origin.