"Grey areas" in large rectal neuroendocrine tumors: when endoscopic ultrasound becomes the silver lining.

A 50-years old male with irrelevant medical history underwent colonoscopy for colorectal cancer screening. On the distal rectum, a subpedunculated (Paris classification Isp) lesion with 15mm was detected. This lesion presented yellowish mucosa and had irregular surfaces, suggesting a subepithelial lesion. Bite-on-bite biopsy confirmed a well-differentiated neuroendocrine tumor (r-NET), positive for synaptophysin, with a low-proliferative index. As r-NETs with 10-20mm fall on a grey area between endoscopic or surgical treatment, a lower endoscopic ultrasound (EUS) was performed, showing a round hypoechoic "salt and pepper" lesion of the mucosa, with focal involvement of the submucosa (3rd layer), but without muscularis propria invasion or regional lymph node involvement (uT1N0). No distal metastases were detected on computed tomography. Thus, the patient was proposed for endoscopic submucosal dissection. With this case we aim to recall EUS importance in large r-NETs, as adequate staging is crucial when deciding optimal therapeutic options.