Malignant Rhabdoid Tumors of the Liver Are Associated With Inferior Outcomes Compared to Other Extracranial Rhabdoid Tumors.

Background Extracranial malignant rhabdoid tumors (eMRT) are rare, highly aggressive pediatric neoplasms. While the liver is a relatively common anatomic site of presentation, the clinical course of patients with hepatic eMRT (eMRT-L) is not well described.Methods We retrospectively analyzed 30 children affected by eMRT-L treated on a consensus regimen provided by the European Rhabdoid Registry (EU-RHAB). Clinical characteristics, radiology features according to the Pre-Treatment Extent of Tumor (PRETEXT) system, treatment details, and outcome were assessed. We employed patients with rhabdoid tumors of the kidney (RTK; n = 30) and other eMRT (n = 60) as controls.Results Median age at diagnosis was 8 months (range: 0-53 months), 16 of 30 patients (55%) presented with metastatic disease. R0 resection was achieved in seven patients (23%). Most tumors showed PRETEXT Stage ≥3 (66%) and frequently exhibited PRETEXT annotation factors. One-year overall and event-free survivals were both 17% (95% confidence interval: 7.5-37). Compared to RTK and other eMRT, patients with eMRT-L had significantly inferior outcomes (hazard ratios 2.47 and 4.39, respectively). Complete resection and absence of metastases were associated with improved survival. Consolidation therapies (i.e., radiotherapy or high-dose chemotherapy) were only rarely used.Conclusions EMRT-L represents a distinct high-risk subgroup within the eMRT spectrum, characterized by inferior survival despite standardized multimodal therapy. Current treatment approaches demonstrate limited efficacy. Our results highlight the urgent need for prospective, collaborative studies to refine risk stratification and to evaluate novel treatment options.