Introduction:
Synchronous colorectal adenocarcinoma with neuroendocrine tumour (NET) are a unique combination of tumours. These may be incidental lesions, usually a histopathological diagnosis rather than a clinical diagnosis from symptoms, examination or even gross appearances.

Aim:
This paper aims to highlight our management strategy on manging a middle-aged woman with synchronous rectal adenocarcinoma and NET.

Case study:
A 53-year-old woman presented with lower gastrointestinal bleeding with constitutional symptoms. Clinical examination and colonoscopy revealed a classical rectal adenocarcinoma, confirmed via biopsy. However, the final histopathology reports of the resected tumour revealed an early rectal adenocarcinoma with synchronous NET.

Results and discussion:
We review the relevant literature and a discussion regarding guidelines available for diagnosis, follow-up and surveillance of this rare case.

Conclusions:
There are no current guidelines for surveillance colonoscopy after detecting gastrointestinal NET, particularly synchronous tumours. NET may be another colorectal cancer risk factor with similar mutations and common genetic markers. Clinicians should consider doing a colonoscopy when or if their patients are diagnosed with any gastrointestinal NET. Detection of any NET warrants a thorough evaluation of the whole colon for colorectal cancer and close surveillance so that timely management can be achieved.