Abstract
Introduction
Renal cell carcinoma (RCC) has a recognized propensity for venous invasion, with tumor thrombus extending from the renal vein through the inferior vena cava (IVC) and occasionally into the right atrium. A renal primary is usually identifiable on cross-sectional imaging. We present an unusual case of high-grade RCC presenting predominantly as extensive Cavo atrial tumor thrombus without a definite renal mass.
Case Info
A 69-year-old man with chronic kidney disease stage 3b and cirrhosis complicated by portal hypertension and recurrent ascites presented with progressive abdominal distention. Imaging demonstrated extensive thrombosis of the intrahepatic and suprahepatic IVC extending into the right atrium, thrombosed hepatic veins, bilateral renal-vein involvement, and bilateral lower-extremity deep vein thromboses. CT angiography showed only an equivocal right renal abnormality without a discrete mass. MRI confirmed extensive thrombus involving the IVC, right atrium, and right renal vein; enhancement within the right renal-vein thrombus raised concern for tumor thrombus. Echocardiography demonstrated large echogenic structures within the right atrium and IVC concerning for mass versus thrombus. Mechanical thrombectomy of the IVC and bilateral iliac veins was performed. Histopathologic examination unexpectedly demonstrated metastatic high-grade renal cell carcinoma, favouring high-grade papillary RCC. Immunohistochemistry was positive for PAX8, RCC, AMACR, CD10, and vimentin and negative for CK7, CK20, GATA3, and CD117, supporting renal origin despite the absence of a radiographically apparent primary. The patient had concomitant extensive venous thromboembolic disease requiring anticoagulation. He was treated initially with heparin and subsequently apixaban, but recurrent bilateral deep femoral thromboses prompted therapeutic enoxaparin. Pembrolizumab and Lenvatinib were initiated. His course was complicated by recurrent ascites, hepatic encephalopathy, progressive renal dysfunction, pancytopenia, recurrent thrombosis, and bleeding. With progressive multiorgan dysfunction and advanced malignancy, care transitioned to comfort-focused management and hospice.
Discussion This case illustrates the diagnostic challenge of RCC presenting primarily as extensive Cavo atrial tumor thrombus without an identifiable renal mass. Enhancement within thrombus and contiguous involvement of the renal veins, IVC, and right atrium should raise suspicion for malignant vascular invasion. Importantly, tumor thrombus must be distinguished from concomitant bland venous thromboembolism because anticoagulation does not treat the malignant component. Histopathologic examination of thrombectomy material may be decisive when imaging is inconclusive.
Conclusion
High-grade RCC can rarely present with extensive Cavo atrial tumor thrombus despite the absence of a radiographically identifiable renal mass. In patients with unexplained extensive venous thrombosis, particularly with renal-vein involvement or thrombus enhancement, tumor thrombus should remain an important diagnostic consideration. Histopathologic evaluation of thrombectomy tissue can be critical when imaging is inconclusive, enabling definitive diagnosis and guiding appropriate oncologic management.