Thromboembolism (TE) is an uncommon problem in children. However, children with cancer have an increased risk of developing TE. A recent study in children with cancers showed overall 8% prevalence of TE compared to 0.7–1.4 events per 100,000 children in the general pediatric population [1–3]. Thrombosis associated with cancer is a multifactorial condition resulting from interaction of cancer, its therapy, and inherent host factors. Figure 10.1 depicts the proposed interaction of various factors responsible for development of cancer-related thrombosis.