Towards a better registration of neuroendocrine neoplasms: The results of the Italian retrospective population-based study

Background: The increasing incidence, rapidly evolving classification, rarity and heterogeneity of neuroendocrine neoplasms (NENs) pose challenges to NEN registration including difficulty in distinguishing neuroendocrine carcinoma (NEC) and neuroendocrine tumours (NETs). Thus, in Italy a higher NEC incidence was reported. Focusing on gastroenteropancreatic (GEP) NEN, we aimed to review GEP NEN, and in particular cases of neuroendocrine carcinoma, not otherwise specified (NOS) and estimate the incidence of NEN, NET and NEC of the GEP. Methods: We launched a pilot study examining cases of neuroendocrine carcinomas NOS (ICD-O3 code 8246) of GEP incidents in the years 2012-2020. Cancer registries (CRs) reviewed information included in the pathology report regarding differentiation and tumour cells proliferation to decide whether to confirm the case as neuroendocrine carcinoma NOS or register it as NET or NEC. After the review, we estimated the GEP NEN, NET and NEC incidence. Results: Nine CRs contributed to the pilot study. After review, in all CRs, only 31% of GEP NOS neuroendocrine carcinomas were confirmed; 50% were recoded as NETs, and approximately 17% of cases were non-NENs. The IR of GEP NENs was 2.99/100,000, and the incidence of NETs was higher than that of NECs. Conclusion: After the review, the incidence of GEP NEN, NET and NEC in the eight Italian CRs involved was comparable to that reported in other European countries. Impact: Our results confirmed that heterogeneity of cancer registries in the registration of NEN requires collaborative work to define and promote a standard definition to be extended to all Italian registries.