Abstract

Background

Tumor thrombus (TT) refers to the direct extension of tumor cells into a blood vessel and is often detected incidentally. It is commonly observed in renal cell carcinoma (RCC), hepatocellular carcinoma (HCC), and Wilms tumor. The presence of TT significantly worsens prognosis and alters disease staging. TT is frequently located in vessels such as the renal vein, inferior vena cava, and portal vein, requiring multidisciplinary evaluation due to its aggressive nature and risk of obstruction or embolization. Diagnostic differentiation between tumor thrombus and a “bland” thrombus (blood clot) typically relies on imaging techniques such as CT or MRI. In this study, we evaluated the association and potential role of circulating tumor cells (CTCs) expressing immune-relevant markers, such as PD-L1, in patients with tumor thrombus. The presence of CTCs originating from TT margins may help refine risk stratification and therapeutic decision-making.

Methods

In this observational study, 12 patients aged 51–80 years with confirmed tumor thrombus were analyzed. The cohort included patients with hepatocellular carcinoma (HCC, n = 4), pancreatic cancer (n = 3), liver cancer (n = 3), renal cell carcinoma (RCC, n = 1), and gallbladder cancer (GB, n = 1). Blood samples were analyzed for the presence of CTCs with PD-L1 expression at baseline, and three patients also had follow-up samples. Samples were processed using the CDSCO-approved OncoDiscover CTC enrichment technology. CTCs were identified using an automated Zeiss microscope based on EpCAM⁺, CK18⁺, DAPI⁺, CD45⁻, and PD-L1⁺ markers.

Results

A total of 16 CTCs were detected in 10 patients (83.33%) from 1.5 mL blood samples, with counts ranging from 1 to 6 CTCs per patient. At baseline, patients with HCC, pancreatic, RCC, gallbladder, and other cancers showed the presence of PD-L1–expressing CTCs. Follow-up samples revealed persistent CTC positivity, although the number of PD-L1–positive CTCs decreased. The mean CTC distribution was 1.33 for CK18-expressing CTCs. PD-L1–positive CTCs were detected in a substantial subset, with a mean distribution of 0.67 (9 CTCs among 12 patients), indicating immune-evasive potential. CTC clusters were rare and detected in only one HCC patient but persisted during follow-up. Both male and female patients demonstrated comparable CTC positivity.

Conclusion

The presence of CTCs in peripheral blood highlights active tumor cell dissemination from tumor thrombus margins. Although CTC clusters were infrequent, their occurrence may indicate an increased metastatic risk. This study demonstrates, for the first time, the presence of CTCs originating from tumor thrombus margins entering systemic circulation. Further studies are required to better understand their clinical implications.