Recurrent presacral tailgut cyst with mucinous adenocarcinoma and metastasis.

Tailgut cysts (TGCs) are rare congenital lesions arising from incomplete regression of the embryonic hindgut, typically located in the presacral space and more common in females. Although often benign, these cysts carry a risk of malignant transformation. We report a case of a woman in her early 50s who presented with abdominal pain, urinary retention, and tenesmus. Initial imaging revealed a large presacral cystic lesion, and incomplete surgical excision confirmed benign histology. However, the patient returned 6 months later with recurrent symptoms and new-onset lower limb weakness. Repeat imaging showed a recurrent cystic lesion with liver and bony metastases. MRI showed peripheral nodular enhancement of the lesion and enhancing bone lesions. A liver biopsy confirmed mucinous adenocarcinoma. Despite chemotherapy, the disease progressed rapidly, and the patient passed away within 2 months. This case highlights the potential for malignant degeneration in TGCs, which, though rare, carries significant morbidity. Complete surgical resection and follow-up are critical to prevent recurrence and malignancy risk. Further research is needed to study the malignant transformation predictors of this rare entity.