Mapping Misconceptions in Neuroendocrine Tumor Nomenclature: A Scoping Review of National Database Studies and Clinical Implications

In 2010, the World Health Organization (WHO) standardized neuroendocrine neoplasm terminology, dividing these tumors by differentiation into well-differentiated neuroendocrine tumors and poorly differentiated neuroendocrine carcinomas. Registries such as the Surveillance, Epidemiology, and End Results (SEER) program and the National Cancer Database (NCDB) store legacy codes predating this framework, raising concern that registry-based research carries nomenclature errors into the clinical literature. We performed a scoping review of research published in 2012–2022 that used SEER and/or the NCDB to study gastroenteropancreatic neuroendocrine tumors, charting 170 articles (from 1079 citations) against the 2010 classification, with forward citation analysis (OpenAlex, Semantic Scholar) measuring downstream citation exposure. Of 141 assessable studies, 88% (n = 124) applied the nomenclature inaccurately: 82.3% included poorly or undifferentiated neoplasms within neuroendocrine tumor cohorts (mean 18.7% of the cohort) and 9.9% conflated database differentiation grade with WHO proliferation grade; appropriate usage did not improve over time. These discordant studies accumulated 7323 citations across 5145 works, with 87.9% cited by at least one review (1075 distinct reviews) and six cited by major guidelines (NCCN, ESMO, ENETS). Across research published from 2012 to 2022, nomenclature discordance was widespread, persistent throughout the study period, and present in studies frequently cited by the secondary and guideline literature. Because these cohorts incorporate more aggressive and poorly or undifferentiated neoplasms, their aggregate outcome estimates are likely biased toward a poorer prognosis, potentially overstating the aggressiveness of well-differentiated neuroendocrine tumors, particularly for prognostic estimates; this review characterized cohort composition rather than quantifying the effect on any individual study’s outcomes, and whether this bias has, in turn, affected clinical decision-making was not assessed here and remains a hypothesis for future work. Journals and guideline panels should require explicit alignment with current WHO definitions for registry-based studies.