Lessons learned about appendiceal neuroendocrine neoplasms from data analysis of the Belgian Cancer Registry 2010-2015

Background and study aims: Appendiceal neuroendocrine neoplasms (aNENs) are a diverse group of malignant neoplasms of varying biological behavior for which information about management and outcome is sparse, with the majority of available studies being retrospective, including only a limited number of patients, and therefore not necessarily reflecting the reality in the community. In the present study clinical, epidemiological and pathological data of appendiceal neuroendocrine neoplasms in Belgium is provided and compared with current literature. Methods: A population-based study was conducted by linking data of the Belgian Cancer Registry with medical procedures in the Belgian Health Insurance database for patients diagnosed with aNEN between 2010 and 2015. Results: We found an aNEN incidence of 0.97/100.000 person years in Belgium. Neuroendocrine carcinoma of the appendix are rare. Most appendiceal neuroendocrine tumors (aNETs) are small G1 tumors. Positive lymph nodes are often found in tumors larger than 2cm, especially aNET G2. Conclusion: A rapid uptake of changing classifications was seen in the community. However, systematic reporting of risk factors for small aNEN can still be improved and should be stimulated. In 9% of cases, reclassifications had to be made, pointing out that in a retrospective analysis, original pathological reports should be checked for specific parameters, before reliable conclusions can be drawn.