A Case Report on Pulmonary Tumor Embolism in a Patient With a Metastatic Gastrointestinal Stromal Tumor Invading the Inferior Vena Cava: Tumor or Thrombus?

Pulmonary tumor embolism is a highly underdiagnosed entity involving the embolism of tumor fragments into the pulmonary vasculature. The vast majority of cases are diagnosed post-mortem. Here we discuss a rare case of a patient with a long-standing history of metastatic gastrointestinal stromal tumor (GIST) that progressed into a direct invasion of the inferior vena cava. The patient presented with shortness of breath and chest pain and was found to have a pulmonary embolism while on anticoagulation. Clinical and imaging findings strongly suggested tumor embolism. Due to its similarity to venous thromboembolism, pulmonary tumor embolism is challenging to diagnose antemortem. Clues to the diagnosis include the presence of intravascular invasion by the tumor (tumor thrombus), recurrent embolisms on anticoagulation, chronic vascular occlusion, and pulmonary infarction.