Primary Ewing sarcoma of the kidney (ESK) is an exceptionally rare and aggressive malignancy, representing less than 1% of renal tumors. It typically affects young adults and often presents at an advanced stage, leading to a poor prognosis. Diagnosis requires a multidisciplinary approach integrating histopathology, immunohistochemistry, and molecular analysis. A 29-year-old male patient presented with a one-and-a-half-year history of right flank pain and one year of painless, intermittent hematuria. Initial management at a local hospital for a suspected inflammatory lesion was unsuccessful. A contrast CT urogram revealed a large (19 cm), locally invasive right renal mass with aortocaval lymphadenopathy. Histopathological examination of a biopsy specimen revealed a malignant round cell tumor. Immunohistochemistry was positive for vimentin, NKX2.2, CD99, and synaptophysin, confirming the diagnosis of Ewing sarcoma. A staging PET-CT demonstrated metastatic disease involving the liver, inferior vena cava (with tumor thrombus), lymph nodes, and multiple skeletal sites. The patient received eight cycles of alternating VDC/IE (vincristine, doxorubicin, cyclophosphamide / ifosfamide, etoposide) chemotherapy, resulting in a significant reduction in the primary tumor and resolution of the IVC thrombus and skeletal metastases. He subsequently underwent cytoreductive nephrectomy. The final pathology confirmed a 7 cm Ewing sarcoma with negative margins and no lymph node involvement. Unfortunately, the patient did not receive adjuvant chemotherapy and expired four months post-surgery. ESK is a diagnostic and therapeutic challenge. This case underscores the utility of a multimodal approach, where neoadjuvant chemotherapy can effectively downstage even metastatic disease, facilitating surgical resection. However, the overall prognosis remains poor, particularly for metastatic presentations, highlighting the urgent need for more effective and less toxic therapeutic regimens.

BACKGROUND Wilms tumor (WT) development and the ability to form distant metastases are thought to be governed by a wide range of molecular factors, with prominent involvement of microRNAs (miRNAs). However, very few studies have explored alterations in miRNA expression between primary and metastatic WT, and all of them focused on a narrow set of miRNAs. MATERIAL AND METHODS We investigated miRNA expression in primary (10) and metastatic WT (6) and in healthy kidney specimens (10) using formalin-fixed, paraffin-embedded (FFPE) samples. miRNA was extracted from FFPE samples using miRNeasy FFPE Kits by Qiagen. Following reverse transcription, cDNA was amplified using miRCURY LNA miRNA Focus PCR Panels by Qiagen, which included primers against 84 specific miRNA targets, of which 81 were successfully amplified. Expression in metastatic WT was compared with primary tumors and healthy kidney tissue. RESULTS Differential expression was particularly evident for 5 miRNAs (miR-17-3p, miR-34b-3p, miR-34c-5p, miR-375-3p, miR-616-3p). Our findings regarding the miR-34 family seem noteworthy in light of the limited existing literature, which similarly reports elevated expression of these miRNAs in WT, although they are more commonly downregulated in many other cancer types. CONCLUSIONS While the sample size in this study was modest, our findings suggest that metastatic tumors exhibit distinct miRNA expression patterns, which may have value for identifying tumors at risk of metastasis. We encourage further studies to validate or refute the role of the miRNAs proposed here in the development of metastasis.

Von Hippel-Lindau (VHL) disease is a hereditary cancer syndrome predisposing to renal cell carcinoma (RCC), typically considered more indolent than sporadic RCC. The '3 cm rule' has guided nephron-sparing interventions, as tumours smaller than 3 cm rarely metastasise. However, accumulating evidence suggests this paradigm is not universal, with some VHL-associated RCCs demonstrating aggressive biological behaviour despite their small size. We report two cases of aggressive clear cell RCC (ccRCC) in patients with suspected VHL. The first case involved a middle-aged male presenting with bilateral renal tumours, an inferior vena cava tumour thrombus and synchronous liver metastases. He underwent right radical nephrectomy with thrombectomy and contralateral partial nephrectomy, with histopathology confirming ccRCC, WHO/ISUP grade 2, with metastatic deposits. The second case was a young male with a large unilateral renal mass showing sarcomatoid and rhabdoid differentiation, WHO/ISUP grade 4, staged pT3a, consistent with aggressive ccRCC. Both presentations deviated from the traditionally indolent course of VHL-associated RCC, underscoring the heterogeneity of tumour biology. These cases highlight the limitations of strict size-based management, emphasising the importance of vigilant surveillance, histopathological assessment and early genetic evaluation. Recognition of aggressive variants is essential to optimise surgical planning and multidisciplinary management in VHL patients.

The World Health Organization classification of renal cell tumors was updated to its fifth edition in 2022 and incorporated significant changes with contributions from pathologists and radiologists. In the 2022 updated classification, epithelial renal tumors are now divided into six categories. Four of these six categories represent the major subtypes of renal tumors: clear cell renal tumors, papillary renal tumors, oncocytic and chromophobe renal tumors, and collecting duct tumors. Two additional categories, representing relatively rare renal tumors, termed other renal tumors and molecularly defined renal carcinomas, have been introduced. While neoplasms in the other renal tumors category are classified on the basis of their histopathologic features, similar to the major subtypes, molecularly defined renal carcinomas represent a new category based on molecular characteristics. In recent years, the number of these rare subtypes has increased significantly. Many of these relatively rare renal tumors represent conventional subtypes that have been reclassified or renamed. Notably, papillary renal cell carcinoma (pRCC) type 2 has been reclassified as other renal tumors or molecularly defined renal carcinomas. As a result, many tumors in these two categories demonstrate gradual enhancement, similar to the enhancement of pRCCs. However, one or more of the following features may differ from those of typical pRCCs: patient age, growth pattern, nonenhanced attenuation at CT, degree of enhancement, homogeneity, T2 signal intensity, and presence of metastases. Careful evaluation of these features can raise suspicion for a rare subtype and is essential for guiding urologists in determining the surgical strategies and guiding pathologists in selecting appropriate immunohistopathologic and/or genetic tests for accurate diagnosis. [©]RSNA, 2026 Supplemental material is available for this article. See the invited commentary by Davenport and Pedrosa in this issue.

This article reports a case of bilateral renal subcapsular hemorrhage in a 51-year-old female patient with lung adenocarcinoma and multiple metastases after receiving four cycles of combination antitumor therapy with pemetrexed, carboplatin, sintilimab, and bevacizumab. The patient had a pre-existing cystic lesion in the right kidney and developed intermittent fever, hypertension, and anemia during treatment. The diagnosis was confirmed by a renal contrast-enhanced CT scan. Management involved immediate discontinuation of bevacizumab, absolute bed rest, hemostasis, antihypertensive therapy, and other comprehensive treatments. The renal hemorrhage was effectively controlled and gradually resolved. Based on the temporal relationship of medication use and clinical manifestations, the renal hemorrhage was considered to be associated with bevacizumab. In recent years, bevacizumab has been widely used in tumor treatment; however, its adverse effects still require further exploration. Hemorrhage induced by bevacizumab primarily occurs in the respiratory tract, digestive tract, and brain, while renal subcapsular hemorrhage has not been reported. This case suggests that bleeding manifestations caused by bevacizumab are diverse and remain a cause for vigilance.

We report a rare case of a 61-year-old female diagnosed with concurrent Chronic Myeloid Leukemia (CML) and Renal Cell Carcinoma (RCC). The patient had a history of CML treated with imatinib for 4 years, with loss of complete hematological response for 3 months before being diagnosed with RCC and lung metastases. Due to a T315I mutation in the BCR-ABL1 gene, the treatment regimen included a novel combination of Axitinib, Dasatinib, and low-dose nivolumab. The patient showed a remarkable therapeutic response with a complete metabolic response accompanied by a highly significant reduction in the size of the tumor and complete resolution of the metastatic lung lesions, as well as a major molecular response in terms of CML disease control.

Immune checkpoint inhibitors (ICIs), a widely adopted therapeutic option for metastatic renal cell carcinoma, are also associated with a range of immune-related adverse events, some of which can be severe and life-threatening. Here, we describe the case of a 70-year-old man with renal cell carcinoma and brain, lung, and bone metastases who developed ICI-associated encephalitis, which was fatal. Initial computed tomography imaging revealed a 9.8 cm mass in the right kidney, multiple pulmonary nodules, and an osteolytic lesion in the left fifth rib. Brain magnetic resonance imaging revealed metastatic lesions in the right parietal lobe and left lateral ventricle. The patient underwent therapy with pembrolizumab and lenvatinib in combination with stereotactic radiotherapy targeting the brain metastases. On day 20 of treatment, the patient developed a generalized seizure, followed by a rapid deterioration in consciousness. He died the following day. Post-mortem examination revealed widespread lymphocytic infiltration of the brain parenchyma, which was consistent with the diagnosis of ICI-associated encephalitis.

Robot-assisted partial nephrectomy (RAPN) and percutaneous thermal ablation (PTA) are established treatment options for localized renal tumors. While RAPN remains the standard-of-care, PTA is increasingly adopted, particularly in patients unfit for surgery. Evidence on how tumor complexity influences comparative outcomes between these two approaches remains limited. We conducted a systematic review of major database up to December 2025 and meta-analysis. Studies directly comparing PTA and RAPN in patients with localized Renal Cell Carcinoma (RCC) were included. Outcomes of interest included local recurrence (LR), recurrence-free survival (RFS), metastasis-free survival (MFS), cancer-specific survival (CSS), overall survival (OS), estimated glomerular filtration rate (eGFR) variation, and complication rates (overall and Clavien-Dindo ≥ III). When feasible, subgroup analyses were performed according to tumor complexity (RENAL ≥ 7 or PADUA ≥ 8). Seventeen studies encompassing 2516 patients met the inclusion criteria. Patients undergoing PTA were older with higher comorbidity burden than those treated with RAPN. Primary technical failure of the first PTA session occurred in approximately 10.9% of cases. Compared with RAPN, PTA was associated with a significantly higher rate of local recurrence (pooled logRR 0.97, 95%CI 0.65, 1.28) and this finding persisted in intermediate-high complexity tumors (logRR 1.09, 95%CI 0.74, 1.44). RAPN was associated with a significantly lower hazard of recurrence (pooled logHR - 0.92; 95%CI -1.29 to -0.56), whereas the difference did not reach significance in the intermediate-high complexity subgroup (pooled logHR - 0.75; 95%CI -1.6 to 0.1). No significant differences were observed in major complications or short- and long-term eGFR variation between techniques. No significant between-group differences were found for metastatic progression, CSS, or OS. RAPN offers superior local tumor control compared to PTA, including in anatomically complex renal lesions, without an associated increase in major complications or deterioration of renal function. Long-term survival outcomes appear comparable. PTA remains an appropriate therapeutic option for carefully selected high-risk patients. However, the higher local recurrence rate and the requirement for rigorous post-treatment surveillance should be carefully considered within the context of shared decision-making.