Venous thromboembolism is a common and serious complication in cancer, and is associated with a substantially increased morbidity and mortality. Furthermore, VTE may be the earliest sign of cancer. Recent studies, however, fail to show a clinical benefit of extended cancer screening in this patient population. Better risk prediction models are therefore warranted to identify VTE patients who would benefit from a rapid and extensive cancer screening. Inflammation and hypercoagulability are considered hallmarks of cancer, and emerging light is being shed on the potential of various markers of inflammation and coagulation in cancer diagnostics and prognostics. Among the inflammatory and thrombotic processes linked to cancer is the neutrophil release of web-like nuclear chromatin (DNA and histones), referred to as neutrophil extracellular traps (NETs). Driven by the tumor environment, NETs have recently been shown to play a central role in tumor progression, metastasis, and tumor-associated thrombosis.

The investigators hypothesize that an enhanced inflammatory state may be predictive of an underlying cancer in patients presenting with VTE. The present study is an ongoing prospective study with the primary aim to investigate the diagnostic potential of markers of inflammation, including markers of NETs, in detecting occult cancer in patients presenting with VTE. Secondary aims are to include other biomarkers of cancer, and to assess whether any or a combination of these biomarkers may be prognostic of occult cancer, recurrent thrombotic events, mortality, or cancer disease progression in VTE patients with an underlying malignancy.

Inclusion Criteria:

• Venous thromboembolism (thrombosis in the deep venous system of upper or lower extremities or iliac veins and/or pulmonary embolism) as detected by ultrasonography, phlebography, computer tomography, or angiography;
• > 18 years or older;
• Written informed consent

Exclusion Criteria:

• > 2 days after VTE diagnosis;
• No blood withdrawal at baseline

Consecutive patients age >18 years with objectively confirmed venous thromboembolism (thrombosis in the deep venous system of upper or lower extremities or iliac veins and/or pulmonary embolism) diagnosed < 2 days.