Inferior Vena Cava Thrombus Associated With Renal Cell Carcinoma With an Atypical Radiological Presentation: A Case Report.

Renal cell carcinoma (RCC) is characterized by the development of kidney masses, which can lead to various long-term complications. Among the extrarenal manifestations associated with RCC, the formation of a thrombus within the inferior vena cava (IVC) is particularly prevalent due to the substantial tumor burden imposed by the kidneys. In this report, we present an exceptional case involving an 80-year-old male patient who presented with an intravascular thrombus within the inferior vena cava (IVC), which originated from RCC. The diagnosis of RCC was conclusively established through core needle biopsy and subsequent tumor marker staining. Remarkably, despite the confirmation of RCC within the IVC thrombus through biopsy and tumor marker analysis, radiological assessments failed to reveal any discernible renal cell masses within the kidneys. The patient subsequently received treatment for RCC with a combination regimen of cabozantinib and nivolumab, which resulted in a noteworthy improvement in his clinical condition. The presentation of RCC in this report is notably atypical, given that the biopsy of the thrombus yielded definitive evidence of RCC while radiological investigations did not yield any indications of renal masses or a tumor burden within the kidneys that would typically be associated with RCC.