RESUMO
BACKGROUND Gastrointestinal neuroendocrine tumors (NETs) are indolent hormone-secreting pathologic illnesses that can occur throughout the whole digestive tract. They are classified by site and grade. Colon neuroendocrine neoplasm (NEN) is an unusual histologic finding that needs to be further investigated. Well-differentiated (WD) Grade-3 (G3) is a new category of NEN that falls between neuroendocrine tumor (NET) and neuroendocrine carcinoma (NEC). CASE REPORT A 60-year-old man with a past medical history of diabetes mellitus presented with severe anemia and significant weight loss. Tumor markers (CEA and CA 19.9) were unremarkable. Colonoscopy showed a large fungating mass in the proximal part of the ascending colon. Biopsy results suggested colonic adenocarcinoma. Contrast-enhanced computed tomography of the chest, abdomen, and pelvis demonstrated a 5×5 cm ascending colon mass with few locoregional lymph nodes and no distant metastasis. A laparoscopic right hemicolectomy performed and histopathologic examination revealed T4N1, WD-NET G3. Postoperative completion work-up was done. Chromogranin-A was in the normal range and nuclear scans (PET and gallium 68) showed no abnormal uptake or residual disease. Extensive review, expert opinion, and multidisciplinary meetings failed to establish guidelines for adjuvant therapy due to the paucity of data in the literature. CONCLUSIONS Well-differentiated grade 3 NETs of the ascending colon is a rare finding in a rare disease. This entity of NENs is an unmet medical issue on the border between NET and NEC that remains a matter of great debate in terms of establishing an accurate diagnosis and outlining proper management.