Tail gut cysts are rare congenital lesions developing from postanal primitive gut remnants. They are mostly benign but carry a potential of malignant transformation, such as adenocarcinoma, neuroendocrine tumor, adenosquamous carcinoma, and pseudomyxoma peritonei. We present a 39-year-old woman with a neuroendocrine tumor arising within a tail gut cyst. She underwent complete resection in 2011. After 4 years, she was admitted with breast nodules, left proptosis, and gaze difficulties. 68Ga-DOTATATE PET/CT demonstrated extensive metastases including pelvic, lymph node, adrenal gland, bone, retro-orbital, cardiac, breast, skin, and subcutaneous metastases.