Renal cell carcinoma (RCC) is a lethal cancer with aggressive behavior and a tendency to metastasis. Cardiac involvement along the renal vein and inferior vena cava (IVC) is a well-known situation during RCC progression, while in the absence of IVC involvement, clinically evident cardiac involvement is very rare, with only a few cases reported in the worldwide literature.1) Herein we report a case of a 61-year-old female of unusual type of RCC with right ventricular outflow tract (RVOT) mass. The RVOT mass was missed at preoperative echocardiography, but recognized at postoperative echocardiographic evaluation of cardiovascular collapse that occurred during surgical resection of RCC.

A 61-year-old female came to our hospital for left flank pain. Her abdominal computed tomography (CT) scan revealed about 9-cm sized exophytic heterogeneous enhancing mass at the left kidney lower pole suggesting RCC (Fig. 1A). Multiple enlarged lymph nodes at the paraaortic, aortocaval, and retrocrural areas were also found, but there were no evidences of metastasis in the liver, spleen, pancreas, right kidney and great vessels. Bone scan showed no bony metastasis. Non contrast enhanced chest CT showed multiple metastatic lymph nodes at bilateral supraclavicular, mediastinal areas with small amount of pleural and pericardial effusion (Fig. 1B). Transthoracic echocardiographic (TTE) examination demonstrated normal heart size and function but scanty pericardial effusion without hemodynamic significance (Fig. 2, Supplementary movie 1). Although these findings indicated stage IV metastatic RCC, we decided to perform cytoreductive nephrectomy because the patient had good performance status with low metastatic burden at that time. During the operation, decreased blood pressure and subsequent cardiac arrest occurred. After cardiac resuscitation with extracorporeal membrane oxygenation circuit insertion, the patient was consulted to cardiology for the evaluation of cardiac arrest. TTE showed markedly dilated right ventricle (RV) with D-shaped left ventricle suggesting RV pressure overloading and moderate amount of pericardial effusion (Fig. 3A–D, Supplementary movie 2). And it also revealed a 5.5 × 3 cm sized echogenic mass nearly obstructing RVOT (Fig. 3E and F, Supplementary movie 3), which was attributable to her hemodynamic instability. When we reviewed her previous TTE performed 1 month ago, we could recognize small RVOT mass which might be easy to be missed without attention (Fig. 2C and D). Resected left kidney revealed 11 × 10.5 × 8.4 cm sized whitish mass that showed infiltrating growth pattern and extensive necrosis (Fig. 4). Microscopic evaluation of the mass revealed malignant epithelioid cells. Most of them had rhabdoid morphology characterized by large vesicular eccentrically located nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (Fig. 5A). Differential diagnosis included primary sarcoma, such as pleomorphic rhabdomyosarcoma and adult RCC with sarcomatoid and rhabdoid feature. Immunohistochemical stains showed diffuse strong positive for CD10 as well as vimentin and focal positive for pan cytokeratin, epithelial membrane antigen (EMA) and desmin (Fig. 5B–F). So we finally concluded that the renal mass wass sarcomatoid RCC with rhabdoid feature, a rare type of RCC. Although biopsy or operation of RVOT mass was not performed because her family refused another procedure or cardiac surgery, the mass was enough to be regarded as a secondary metastasis of RCC considering the very aggressive behavior of this type of RCC2) and multiple metastases in lymph nodes of both thorax and abdominal cavity. The patient's condition deteriorated and she died 5 days after the operation.

Cardiac metastasis was shown to be present in 11% of patients who died of RCC.3) The extension of a tumor into the renal vein or IVC as a luminal mass, with the growth along the caval wall into the right heart chambers, has been well documented as the most common mechanism of cardiac metastasis of RCC. Nevertheless, cardiac involvement of RCC without IVC involvement, as in our case, can present. Zustovich et al.1) analyzed these cases and suggested another patterns of RCC metastasis to the heart; through the intrathoracic lymphatic systems, especially in the presence of disseminated disease. The latter is speculated as a metastatic pathway of our case, because in our case, intrathoracic lymph node metastasis and pericardial effusion was demonstrated.

A search of the literature revealed several cases of solitary RV metastasis of RCC without IVC involvement,1) but there has been only one case of metastasis confined to RVOT.4) In this case, the metastasis was confirmed after 5 years after a radical nephrectomy and treated by echo-guided percutaneous coil embolization. To the best of our knowledge, our case is the first case that primary RCC and RVOT metastasis without involving IVC or right atrium were discovered almost simultaneously.

Another unique point of our case is the rare pathologic type of RCC, rhabdoid variants which represents dedifferentiation or divergent differentiation of RCC.5) Recognition of this type has prognostic implications as it is associated with rapid progression and poor prognosis. Sarcomatoid RCC can metastasize unusual sites including breast,6) colon and oropharynx.7)8) But cardiac metastasis from sarcomatoid RCC is very exceptional.

RCC with rhabdoid feature is a rare type of RCC that carries aggressive behavior with high metastatic potential and short survival time. When this type of pathology is confirmed, complete cardiac evaluation should be done in patients with RCC, especially in the presence of pericardial effusion. In addition, we should pay more attention to other cardiac and pericardiac structures such as great vessels and mediastinum which can be unpredicted metastatic sites if signs of metastasis around these structures are present.