Imaging tumor thrombus across malignancies: current concepts and the expanding role of PET/computed tomography

Tumor thrombus (TT) represents the intravascular extension of the tumor, most commonly seen in renal cell carcinoma (RCC) and hepatocellular carcinoma (HCC). It is clinically significant with direct implications on staging, prognosis, and therapeutic decision-making. TT is most commonly noted in RCC and HCC, but can also occur in several other malignancies, such as adrenal cortical carcinoma, colorectal carcinoma, pancreatic neuroendocrine tumors, thyroid carcinoma, and testicular carcinoma. Differentiating TT and bland thrombus is crucial. Surgical resection offers survival benefit in select cases, whereas systemic therapies, including immunotherapy and targeted agents, are transforming the management of RCC and HCC with vascular invasion. TT is a marker of aggressive tumor biology that significantly worsens the prognosis. This review highlights current knowledge about the pathogenesis, imaging features, prognostic impact, and therapeutic approaches to TT, with emphasis on the evolving role of nuclear medicine, and provides a narrative review of peer-reviewed literature and available guidelines.