Threads and streaks sign | Radiology Signs

The threads and streaks sign occurs due to a vascularized tumor thrombus (growing tumor cast) extending into the portal vein, and sometimes the hepatic veins or inferior vena cava, from hepatocellular carcinoma (HCC). This tumor thrombus is infiltrated and supplied by tumor neovascularity, creating multiple fine linear vascular channels within the involved vessel lumen, originally described on celiac angiography and now also recognized on contrast-enhanced ultrasound, CT, and MRI.

Why is it called so?

It is named “thread and streaks” because on angiography the tumor-supplying vessels growing within the thrombus appear as multiple thin, thread-like linear contrast streaks coursing along the occluded vein, contrasting with the surrounding non-opacified thrombus. The term was coined by Okuda et al. in their 1975 Radiology description of growing hepatocellular carcinoma casts in the portal vein.

Pathophysiology

The sign arises from tumor growth into the vessel lumen forming a tumor thrombus supplied by neovascularization. These vessels create linear enhancing channels inside the thrombus during the arterial phase of imaging, resulting in the characteristic thread-like vascular pattern. This reflects active tumor angiogenesis and direct intravascular tumor extension, distinguishing tumor thrombus from bland (non-vascularized) thrombus.

Alternative names: Thread and streak sign; striated vascular sign (both describing the same finding in HCC portal/hepatic vein tumor thrombus).

Other associated named signs: None specifically linked, but the sign is used alongside other CT/MRI criteria (thrombus enhancement, expansile vein, neovascularity on Doppler) to distinguish tumor thrombus from bland thrombus.

References

1. Okuda K et al. Demonstration of growing casts of hepatocellular carcinoma in the portal vein by celiac angiography: the thread and streaks sign. Radiology. 1975.