The majority of genetic studies have excluded individuals with cancer-related thrombosis, and the relatively few studies that have been performed (which have mainly focused on the factor V Leiden and prothrombin G20210A genetic variants), have reported conflicting results.1, 11, 12, 28–30 These discrepancies are most likely due to the use of a single-marker, and inherent problems of low statistical power and poor reproducibility. The gene discussed is F5; the disease is cancer.