INTRODUCTION: Rectal duplication cysts are rare cystic lesions, arising from the hindgut and classified as congenital/developmental tumors of the presacral space. Their clinical presentation is nonspecific, the diagnosis remains difficult and their management is aided by a multidisciplinary evaluation. CASE REPORT: We report the case of a 55-year-old woman with a cystic mass located in the retrorectal space and identified incidentally on a CT scan. Following imaging studies, surgical resection by a posterior approach (Kraske procedure) was carried out and an adenocarcinoma arising in a duplication cyst of the rectum was present an uncommon case of a rectal duplication cyst with malignant transformation and distant metastasis, describe the clinical, radiologic and pathologic findings and discuss tidentified by microscopy. CONCLUSION: We phe embryological basis of rectal duplication cysts and the surgical anatomy of the presacral space.