Background: Retrocecal hamartomas are rare cystic lesions due to the persistence of the tailgut. Sometimes the epithelial or mesenchymal components of the cyst wall undergo neoplastic transformation, and, within them, carcinomas and sarcomas can develop. Case Presentation: We present the case of a multicystic lesion, discovered in a patient with perineal pain, which the imaging investigations have localized in the retrocecal space. The histological evaluation performed on his excisional biopsy demonstrates a retrocecal hamartoma harboring a neuroendocrine neoplasm. Conclusion: Tailgut cysts (TGC) are quite rare, only sometimes symptomatic, and infrequently, they also undergo a malignant transformation; in particular, the literature reviews report a higher frequency of adenocarcinomas. The differential diagnosis between lesions with different prognoses and pathogenesis that can develop in the retrocecal space requires a histological examination, which in some cases, becomes essential if we consider the potential for metastatic and local recurrence of any malignant neoplasm that arose in this site.

Keywords: Neuroendocrine tumor, retrorectal hamartoma, tail-gut.