Meta-analysis finds MyoD1 immunopositivity common in retroperitoneal spindle cell/sclerosing rhabdomyosarcoma

This study combined a meta-analysis of global literature (403 unique Sc/SRMS cases) with an institutional case series from Peking University International Hospital (12 adult patients) to characterize the clinical, pathological, and molecular features of retroperitoneal spindle cell/sclerosing rhabdomyosarcoma (Sc/SRMS). The intervention or comparator was not reported. The institutional cases typically presented with large, high-grade retroperitoneal tumors that frequently invaded adjacent organs.

In the institutional series, MYOD1 mutations were detected in 33.3% of patients. Immunohistochemical analysis showed MyoD1 immunopositivity in 92% of these cases, which was significantly greater than myogenin immunopositivity at 42% (P value reported). Safety, tolerability, and specific follow-up data were not reported.

Key limitations include the study's design as a meta-analysis and retrospective case series, which inherently limits causal inference. The rarity of retroperitoneal Sc/SRMS makes it exceptionally uncommon and poorly characterized. The practice relevance is not explicitly stated, but the findings contribute descriptive data on a rare tumor subtype. Clinicians should recognize that this evidence is observational and preliminary for this specific anatomical site.