Lymphoma typically manifests as lymphadenopathy, with or without solid organ involvement. Lymphomatous masses tend to respect anatomical structures, encasing rather than invading them. Tumor thrombus formation is a rare presentation in lymphoma that has been previously described in the liver and kidneys. We report an unusual presentation of B-cell lymphoma with imaging findings suggestive of metastatic lung cancer with tumor thrombus in the pulmonary vein and left atrium.