Primary mesenchymal chondrosarcoma of the kidney without HEY1-NCOA2 and IRF2BP2-CDX1 fusion: A case report and review

Mesenchymal chondrosarcoma (MC) of the kidney is rare. To the best of our knowledge, the current report is the first case of a giant extraskeletal MC that arose primarily from the right kidney and mimicked renal cell carcinoma at the locally advanced stage (cT3bN0) with vena cava thrombus and multiple pulmonary arterial tumor emboli. Additionally, the literature on renal EMC is reviewed and the possibilities of oncogenic heterogeneity are discussed. A 64-year-old woman was admitted to Yamagata University Hospital for sudden onset of asymptomatic gross hematuria. CT revealed a 90 mm renal mass without calcification in the right kidney and tumor thrombus extending to the inferior vena cava. Radical nephrectomy with thrombectomy was performed. Lung metastasis was detected 2 months later. The patient received systemic chemotherapy, which was only marginally effective. She died of the malignancy 8 months after surgery. Microscopic examination of the tumor revealed typical histology of MC and a lack of HEY1-NCOA2 and IRF2BP2-CDX1 gene fusions in the tumor tissues. Not all MC patients may exhibit chromosomal alterations in the tumor, suggesting the presence of genetically heterogeneous pathways of MC oncogenesis. Further studies are required to confirm the present findings and reinforce the molecular diagnosis of MC.