Approaches to Ultra-Rare Sarcomas: Definitions, Diagnostics, and Therapies

Ultra-rare sarcomas are sarcomas with an incidence of 1 case per million inhabitants per year, in which rarity poses a barrier to conducting histotype-specific randomized studies. This manuscript provides practical information and reference for clinicians and researchers looking to develop an understanding of the complexity, worldwide discrepancies in treatment options, and management choices for these patients. We provide definitions, diagnostic challenges, and therapeutic approaches to ultra-rare sarcomas. We highlight existing discriminations faced by patients with ultra-rare sarcoma, differences in approval status for innovative agents, and future perspectives for sarcoma experts who aim at working for a change in the field.