Rare diseases are defined by their low prevalence. In Europe, a disease is considered rare if it affects fewer than 1 in 2000 people. A more specific definition exists for rare tumours, which are classified as malignancies with an incidence of fewer than 6 per 100,000 per year. This classification, established through EU-funded projects and the Joint Action on Rare Cancers (JARC). Population-based cancer registries provide essential epidemiological indicators—incidence, prevalence, survival, and mortality—allowing continuous assessment of the cancer burden in defined populations. Projects such as RARECARE, RARECAREnet and EUROCARE have contributed to understanding rare cancer epidemiology across Europe. Rare gynaecological cancers, including non-epithelial ovarian tumours, epithelial tumours of the fallopian tube, and placental choriocarcinoma, exhibit varying incidence and survival figures, with older women often more affected and five-year survival generally lower than common gynaecologic cancers. The European Reference Networks (ERNs), established in 2017, connect centres of expertise to improve care, facilitate teleconsultations, and promote research, education, and guideline development. National and international rare cancer registries, including clinical databases with molecular data, are vital for harmonising treatment, optimising patient referral, and enhancing outcomes. Accurate, interoperable cancer registration supports health policy planning, resource allocation, and global assessment of rare tumour burden, which remains limited in low- and middle-income countries. Prospective, comprehensive registries are essential for advancing rare cancer management worldwide.