Remote malignant intravascular thrombi: EUS-guided FNA diagnosis and impact on cancer staging

Background and Aims: Malignant vascular invasion usually results from gross direct infiltration from a primary tumor and impacts cancer staging, prognosis, and therapy. However, patients may also develop a remote malignant thrombi (RMT), defined as a malignant intravascular thrombus located remote and noncontiguous to the primary tumor. Our aim was to compare EUS, CT, and magnetic resonance imaging (MRI) findings of RMT and to explore the potential impact on cancer staging. Methods: Patients with RMT were identified from a prospectively maintained EUS database. Retrospective chart review was performed to obtain EUS, CT/MRI, clinical, and outcome data. Results: A median of 3 FNAs (range, 1-8) was obtained from RMT in 17 patients (60 ± 14.1 years, 56% men) between April 2003 and August 2016, with the finding of malignant cytology in 12 patients (70.6%; 10 positive, 2 suspicious). CT/MRI detected the RMT in 5 patients (29.4%), 4 of whom had positive or suspicious EUS-FNA cytology. Among the 8 newly diagnosed pancreatic adenocarcinoma (PaC) patients, CT did not detect the RMT in 5 (63%), of whom 3 patients had positive or suspicious intravascular EUS-FNA cytology. For newly diagnosed PaC patients (n = 8), the EUS-FNA diagnosis of a biopsy specimen-proven RMT upstaged 3 patients (37.5%) and converted 2 patients (25%) from CT resectable to unresectable disease. No adverse events were reported. The mean follow-up was 18.9 ± 27.7 months. Conclusions: Our study demonstrates the ability and potential safety of intravascular FNA to detect radiographically occult RMT, which substantially impacts cancer staging and resectability.