Discussion
Renal cell carcinoma is an aggressive tumor that classically presents with flank pain, abdominal mass, and hematuria only in advanced cases. According to the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) program, there will be an estimated 73,750 new RCC cases in the U.S. in 2020, constituting 4.1% of all newly diagnosed cancer cases.10 Data for 2021 is not available to date. RCC mostly presents as a localized or locally advanced mass, and about 30% of patients have disease metastasized to different sites at the time of diagnosis. The most common metastatic sites are the central nervous system, adrenals, lungs, liver, and intra-abdominal structures. The heart is an uncommon and atypical site of metastasis for RCC with an incidence of 1.3-4.2%.13 The primary histopathological type of cardiac metastasis is the clear cell RCC. The primary mechanism of RCC metastasis to the heart is a direct extension of intravascular tumor growth into renal veins and inferior vena cava, thus seeding the heart tissue. RCC has a high propensity to invade local vasculature extending to renal veins and inferior vena as a solid column, with 1% of cases having extension up to the right atrium level. In our patient, the imaging studies showed that the left lower kidney mass had contiguous extension across the renal vein with continuous extension into the inferior vena cava tracking cranially to cavo-atrial junction partially protruding into the right atrium. Our patient’s unique feature was the extension of the tumor in the caudal direction inferior to the renal veins in the distal inferior vena cava, bilateral common iliac veins, and external iliac veins. No such extension has been demonstrated in the published data.
Management of RCC, either medically or surgically, depends on the stage of the disease. CT scan and magnetic resonance imaging (MRI) are preferred imaging modalities for staging the disease, with MRI being the gold standard.14 Echocardiography and CXR are used to locate and explore cardiac disease. In our case, the CT scan revealed findings, as mentioned above. Echocardiography showed a plump shaped mass protruding from the IVC in the right atrium, measuring 2.8 cm into 3.1cm. Surgical resection of tumors with nephrectomy and removal of IVC thrombus is the standard of care but only in patients with expected good performance status as the procedure is associated with significant morbidity and mortality.14 Patients who are not surgical candidates, as our patient, due to extensive disease or contraindications to surgery, are managed with chemotherapy, hormonal or radiation therapy; however, targeted therapy with agents like ipilimumab, nivolumab sorafenib, sunitinib, temsirolimus, everolimus, and axitinib is the standard of care these days. Ipilimumab plus nivolumab showed superior efficacy over others.15However, the long-term prognosis is dismal in metastatic RCC with prognosis in months even with aggressively targeted immunotherapy.