Tumor thrombus is defined as tumor extending into a vessel, typically a vein. It occurs in a wide variety of malignancies. It is vital to distinguish tumor thrombus from "bland" thrombus (free of neoplastic cells) in the setting of neoplasia, as this often impacts staging and treatment approach.
Tumor thrombus is usually composed of a soft tissue component and a thrombotic component.
Tumor thrombus is perhaps most frequently associated with renal cell carcinoma, where tumor may invade the renal vein and grow caudally into the right atrium. However, this phenomenon is not isolated to renal cell carcinoma, and is recognized in :
- hepatocellular carcinoma
- Wilms tumor
- adrenal cortical carcinoma
- retroperitoneal tumors
- transitional cell carcinoma of renal pelvis (rarely)
Contrast-enhanced ultrasound is reported to be 100% sensitive and specific. The key feature of portal vein tumor thrombus is the presence of enhancement or color Doppler flow within the thrombus .
Imaging features consistent with tumor thrombus on contrast-enhanced CT and MRI include:
- presence of enhancement , the most specific sign
- appearance of vessel expansion
- diffusion restriction
Streak and thread appearance of the tumor thrombus is characteristic in angiography due to parallel opacification of small vessels and arterial-venous shunting .
Increased activity associated with the presence of thrombus on CT
Treatment and Prognosis
In hepatocellular carcinoma (HCC), surgical resection is rarely performed in the setting of tumor thrombus given poor underlying liver function and high rate of recurrence even after liver transplant. For that, it is considered absolute contraindication to liver transplantation .