INTRODUCTION:
Children with cancer are at increased risk for venous thrombosis (VT) or venous thromboembolism (VTE).  This complication can manifest as bland thrombus or tumor thrombus1,2. Tumor thrombus is defined as the extension of the tumor into the vessel lumen, typically a vein. Incidence of tumor thrombus varies depending upon the type of cancer3. In children, it is most widely reported to be associated with Wilms tumor4,5. Although pathologic exam is the reference standard, imaging is very reliable and helps in early detection of tumor thrombus, without the use of any invasive technique6.
Bland thrombus on the other hand, is a fibrin clot without neoplastic cells which may occur in patients with or without an underlying malignancy. Bland thrombus is thought to result from the interaction of various factors such as cancer type, presence of central venous catheters, chemotherapy and acquired or inherited prothrombotic defects, among others1. Cancer can also contribute to the development of bland thrombus by mechanical effects on the venous flow, as in those with solid tumors2. It is unknown if intravascular extension or tumor thrombus increase the risk for bland thrombus formation. Anticoagulation is sometimes administered in conjunction with cancer-directed therapy to this group of patients.
Available literature describing the treatment characteristics and outcomes of pediatric patients with solid tumor-associated tumor thrombus is limited, and there are no evidence-based studies to guide management. The purpose of this study is to describe the role of anticoagulation in patients with tumor thrombus. We performed a retrospective review at a large pediatric tertiary care center to evaluate the clinical and treatment characteristics of patients with tumor thrombus, indications for starting anticoagulation, and rate of bland tumor formation and bleeding events for those treated with and without anticoagulation.