Introduction & Objectives: The established paradigm that SRM metastatic risk correlates with tumour size has guided contemporary management approaches favouring active surveillance and nephron-sparing strategies for smaller lesions. However, rare aggressive presentations warrant re-examination of risk stratification models. We present three cases of metastatic SRMs that challenge current prognostic frameworks and demonstrate atypical metastatic patterns requiring urological consideration for comprehensive staging protocols.
Methods: We conducted a retrospective case series analysis of three patients with metastatic SRMs who presented at Royal Darwin Hospital during 2024/2025. All patients underwent comprehensive imaging including CT, MRI, and PET scans. Histopathological examination with immunohistochemistry was performed on tissue samples obtained through biopsy or surgical resection. Patient demographics, clinical presentation, imaging findings, pathological results, and treatment outcomes were systematically reviewed.
Results: Three male patients (aged 51, 67, 59 years) with SRMs measuring 40 mm, 35 mm, and 34 mm respectively presented with synchronous metastatic disease exclusively to bone. Case 1: clear cell RCC with neurological compromise from spinal metastases requiring urgent surgical stabilisation. Case 2: papillary RCC Grade 2 with widespread sclerotic lesions initially suspected as alternative pathology. Case 3: clear cell RCC with extensive osseous involvement discovered incidentally during chest pain evaluation. Remarkably, despite different histological subtypes (two clear cell, one papillary type 2), all demonstrated bone-only metastatic patterns without pulmonary, hepatic, or nodal involvement—contradicting established metastatic distribution patterns for RCC subtypes.
Conclusions: These cases demonstrate that size-based risk stratification may inadequately predict metastatic potential in select SRM patients. The unexpected bone-exclusive metastatic pattern across different RCC subtypes suggests unidentified molecular pathways influencing organ tropism. For urological practice, these findings support comprehensive staging evaluation for all renal masses regardless of size, particularly when clinical presentation suggests systemic disease. Future genomic analysis may identify biomarkers enabling better risk stratification and personalised surveillance protocols for high-risk SRMs, ultimately refining patient selection for active surveillance versus immediate intervention.