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.