304 First Reported Case of Metachronous Tumours With Delayed Recurrence from The Neuroendocrine Tumour Arising in A Tailgut Cyst

Abstract

Abstract Background Malignant transformation of tailgut cysts (benign retrorectal cysts) into Neurodendocrine tumours (NETS) is extremely rare with less than 30 reported cases in the literature. A tiny proportion of these cases report early recurrence (within 2 years) and to our knowledge none have reported delayed recurrence 6 years after primary resection. Case history We report a 55-year-old male who underwent laparoscopic excision of a 5 cm presacral tumour found incidentally and confirmed histologically to be a G1 NET (WHO Classification) arising from a pre-existing tail gut cyst, with no evidence of metastasis.16 months later the patient presented with bowel obstruction secondary to adenocarcinoma of the colon at the splenic flexure. The patient underwent laparoscopic left hemicolectomy; histology confirming a moderately differentiated adenocarcinoma (TNM stage pT3pN0). The patient underwent adjuvant chemotherapy post-operatively based upon immunohistochemistry. The patient was followed up for both tumours with CEA, serum chromogranin A, colonoscopies, and CT scans. At 5th year post hemicolectomy, CT scan revealed a new asymptomatic 18 mm left internal iliac lymph node which was avid on octreotide scan consistent with metastasis secondary to NET resected previously. He, therefore, underwent 30Gy sabre radiotherapy. Conclusions There is no consensus regarding follow up duration post early NET resection. The recurrent NET was picked up incidentally as part of the 5-year colorectal adenocarcinoma follow up at our unit. The recurrent NET would not have been identified had this not been a metachronous case. Thus, consideration must be given to both radiological and biochemical follow up post NET resections.