Pulmonary Tumor Embolism Diagnosed by Endobronchial Ultrasound

To the Editor: Pulmonary tumor embolism (PTE) is a diagnostic challenge. It can be microscopic or macroscopic and is clinically indistinguishable from pulmonary venous thromboembolism. We present a case of PTE diagnosed using endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). A 66-year-old woman was referred for evaluation of a right hilar fullness. She had mild dyspnea on exertion with no associated chest pain, palpitations, cough, hemoptysis, leg swelling, fever, chills, or syncope. Her history included renal cell carcinoma with inferior vena cava extension for which she underwent right nephrectomy and resection of endovascular tumor in 2004, pulmonary embolism treated with anticoagulation, and hypertension. She had no history of tobacco, alcohol, or illicit drug use. Her physical examination was unremarkable. Computed tomography scan of the chest reported right hilar soft tissue density described as extrinsic to the pulmonary artery (Fig. 1), but we could not exclude an endoluminal process. She underwent bronchoscopy with EBUS-TBNA to exclude hilar nodal metastases (Fig. 2A). Ultrasound examination with Doppler showed the density within the pulmonary artery (Fig. 2B).FIGURE 1: Computed tomography scan of the chest showing defect in the right pulmonary artery.FIGURE 2: Endobronchial ultrasound of the right pulmonary artery showing intraluminal density (A) and Doppler ultrasound (B).Previous vascular invasion added tumor embolism to the differential, and EBUS-TBNA was deemed the least invasive means of confirmation. Samples were collected under real-time EBUS guidance with a 22 G needle, and cytology examination showed renal cell carcinoma with abundant red blood cells. Tumor cells stained for vimentin and epithelial membrane antigen, and were negative for thyroid transcription factor-1 and cytokeratin 20 (Fig. 3).FIGURE 3: A, Hematoxylin and eosin stain showing tumor cells with clear cytoplasm surrounded by red blood cells (×400). B, Tumor cells positive for vimentin (×400).PTE in autopsy studies is a relatively common event and often an unrecognized complication of malignancy. There have been few reported cases of tumor emboli since Schmidt1 first described PTE in 1897. Incidence in several autopsy studies of patients with carcinoma has been reported to be 3% to 26%.2,3 The likelihood of PTE depends on the underlying malignancy. PTE can be macroscopic or microscopic and occurs when aggregates of tumor cells lodge into the pulmonary vasculature. Pulmonary vessels can be occluded by large tumor emboli and is clinically indistinguishable from pulmonary thromboembolism, which may have been the case in our patient with a history of pulmonary embolism. PTE can also cause lymphatic obstruction and occlude small arteries or arterioles. Cancers that commonly cause tumor embolism include liver, breast, gastric, renal, prostate, and choriocarcinoma.2–5 Symptoms and physical findings are indistinguishable from that of venous thromboembolism. Several cases have been reported using various modalities for diagnosis. Chest radiographs are usually normal but may show cardiomegaly and prominent pulmonary vasculature (reported in <50% of cases).2,5 Ventilation-perfusion radionuclide scans may show a characteristic “segmental contour pattern” or small peripheral subsegmental perfusion defects.6 Computed tomographic pulmonary angiography may reveal dilated and beaded peripheral arteries.6 Right ventricular strain and elevated pulmonary artery pressures can be seen on echocardiogram. All of these can also be seen in venous thromboembolism. A wedged pulmonary artery catheter can also be used to obtain cytology specimens to make the diagnosis.7 Our approach of obtaining cytology specimens with real-time EBUS-guided needle aspiration is less invasive. To our knowledge this was the first reported case of PTE diagnosed by EBUS, which was presented at the 2011 ATS meeting8; since then there have been several case reports describing the utility of EBUS in diagnosing PTE.9,10 EBUS is used to diagnose mediastinal and hilar diseases such as lung cancer, lymphoma, and sarcoidosis. Pulmonary arteries can be evaluated using EBUS, and, recently, Aumiller and colleagues performed a pilot study and detected 97/101 (96%) pulmonary emboli using EBUS. EBUS not only helped evaluate the pulmonary artery with direct imaging, but, in this case, aspiration for cytology was performed without significant bleeding or complications with minimal risk.11 We suggest that this procedure be considered by those with significant EBUS-TBNA experience in the rare patient considered to have PTE. Neeraj R. Desai, MD Sara R. Greenhill, MD Mary Vance, APN Kevin L.