Cancer care for head and neck cancers is multidisciplinary and complex and knowledge on the rare ones is limited. There is a wide consensus that to support clinical research on rare cancers, clinical registries should be developed within networks specializing in rare cancers. Our hypothesis is that our head and neck cancer registry established in the framework of the European reference network on rare adults solid cancers will help to: describe the natural history of rare head and neck cancers; evaluate factors that influence prognosis; assess treatment effectiveness; measure indicators of quality of care. The registry is a prospective observational real-world registry. It collects data from already available registries/database and/or directly from expert health care providers (HCP). Information are prospectively collected on patient characteristics; exposure, outcomes and potential confounders (https://euracan.eu/research/starter/rare-head-and-neck-cancer-registry/#codebook). The registry if federated (i.e. data are stored by the data provider). Analyses will be performed using the federated learning approach which split computations into a local part and a central part. The data providers will share sub-computations only. Data quality checks are envisioned to assess whether data value are present, valid and believable. Validity and plausibility checks are embedded in the electronic case report form (CRF) in the form of alerts and errors during the data input. Additional checks are implemented in R and run using the federated learning to ensure a central data quality monitoring. The data analyses will include descriptive statistics showing frequency and patterns of patients' and cancers' variables; analytical analyses investigating the association of patients/disease and/or treatment characteristics and health outcomes. Fondazione IRCCS Istituto Nazionale dei Tumori (INT) is the coordinator of the EURACAN registry as well as a data provider. At the INT, and at each HCP involved, responsible investigators ensure that the EURACAN registry will be implemented in compliance with the protocol, following the instructions and procedures described herein. Each HCP is a controller and will identify a data processor. The processing of patients' personal data taking part in the registry is compliant with local privacy legislation and the General Data Protection Regulation 2016/679 of the EU.