AB203. 147. The complexity of a carcinoid tumour

Abstract: Carcinoid tumours are the most common form of neuroendocrine tumour and carcinoid tumours of unknown origin (CUO) are the rarest subgroup, accounting only for 10%1. Utilisation of 68-gallium Dotatate PET-CT offers increased sensitivity and characterization of CUO, compared to traditional Octreotide scans2. However, the rarity of CUO has led to paucity in guidelines as to how to manage recurrent local metastatic disease. We describe a case of CUO with recurrent, metastatic disease treated with surgical excision. A 55-year-old woman was referred with a 4-month history of proctalgia and obstructive defecation. Digital rectal exam (DRE) revealed a posterior retro-rectal mass. CT and biopsy as well as octeotide scan and elevated serum chromogranin A. Laparoscopic ultra-low anterior resection with ileostomy formation was performed. Eighteen months post-op, surveillance CT TAP highlighted an enlarged lymph node in the right external iliac chain, which was octreotide avid on gallium PET-CT. Following multidisciplinary team (MDT) input, a robotic-assisted right obturator lymph node resection was undertaken after which post-operative histology confirmed metastatic well-differentiated neuroendocrine tumour. Thorough DRE is essential in the setting of rectal symptoms. Multidisciplinary management and adherence to internationally accepted best practice is essential in rare conditions like CUO. Regular surveillance will continue.

Keywords: Carcinoid of unknown origin; gallium PET; local metastasis; recurrence