A rare gastric lesion: diminutive, well-differentiated, Grade 3, type 3 gastric neuroendocrine tumor with extremely high ki-67 index removed en bloc under endoscopy.

Grade 3, type 3 gastric neuroendocrine tumor (g-NET) shows specific features of clinical interest and the therapeutic management of the lesion is not yet completely standardized. We present the unusual case of a 34-year-old male patient with a diminutive (less than 0.5 cm), well-differentiated, G3, type 3g-NET with extremely high Ki-67 index (higher than 80%). The lesion was subsequently removed en bloc via endoscopic submucosal dissection. Regarding the proliferation rate, Ki-67 index values usually range from 21 to 50%, and less commonly above 55%, in G3 NET. To our knowledge, this lesion represents a small size with the highest Ki-67 index diagnosed with G3 g-NET. However, as g-NET might recur even after a long duration, we recommend a long-term follow-up, such as 10 years after complete resection in patients to evaluate the endoscopic resection approach.