Pleomorphic and spindle-cell/sclerosing rhabdomyosarcoma (P- and S-RMS) are ultra-rare sarcoma subtypes that differ biologically and clinically from the more common pediatric forms of rhabdomyosarcoma. Affecting primarily adults and occurring at a rate of fewer than one case per million, these tumors have limited clinical evidence and few dedicated studies.

The Ultra-rare Rhabdomyosarcoma Working Group was established to address this unmet need by consolidating global expertise, harmonizing classification criteria, and promoting both clinical and translational research for these distinct but related sarcoma subtypes. The group’s goal is to generate meaningful evidence that improves understanding, informs treatment, and supports the development of precision medicine approaches.

Our Objectives
The Ultra-rare Rhabdomyosarcoma Group seeks to characterize the clinical course, molecular landscape, and treatment outcomes of pleomorphic and spindle-cell/sclerosing rhabdomyosarcoma through international collaboration. By correlating genomic features with clinical behavior, the team aims to refine disease classification and identify potential therapeutic targets.

Our Core Initiatives

• Collect multicenter data to define clinical behavior and treatment outcomes.


• Investigate molecular and genomic drivers, resistance mechanisms, and therapeutic opportunities.


• Establish an international registry to capture prospective clinical and translational data.


• Advance research linking molecular alterations with clinical outcomes to guide targeted therapies.