Each participating site will have access through the reserved area of webpage www.ita-net.org, where a proper link is enabled for the data recording in a database which ENETS set-up for the participating Sites in Europe, the ENETS-registry (https://www.enets-registry.eu/enets/).

The eligible patients, visited at each participating site, will be asked to adhere to the ENETS-project through a proper Informed Consent obtainment procedure.

The data will be collected in an anonymised way. Each patient will be identified by a code.

The data management and quality check of the Italian data is deputed to ITANET. The data will be collected in a prospective way, both for the new diagnoses (first visits) and for the follow up visits of patients with already acquired diagnosis. The enrolment will take place during the outpatient visit or at the time of the hospitalisation for the NET-related surgery.

Of course, considering the observational nature of the study, the follow up visits will be planned on the basis of each patient's clinical need, which is different patient by patient, according to the disease staging, the primary tumour location, the eventual surgery.

The data flow will be the following:

• The participating site records the data in the database, waiting to be validated;
• ITANET has the role to check the recorded data for completeness and coherence in order to decide whether:
  1. The data are acceptable: in this case the validated data will be acquired from ENETS-registry;
  2. There are discrepancies: in this case a query will be sent to the related site in order to check, correct/explain where applicable and to resubmit the data. The process starts again until final validation.

The data will be collected yearly to provide several information, such as:

• Type of NETs followed by the reference national sites for the management of the study pathology;
• Tools used for the diagnosis definition and the disease staging;
• Therapeutic approach (surgical or medical);
• Disease trend during follow up.