Evaluating the Role of EUS-FNA in the Diagnosis of Metastasis to the Pancreas: Results From a Tertiary Cancer Center

Abstract

Introduction: Metastasis to the pancreas is less than 5% of all tumors detected in the pancreas. Accurate diagnosis of isolated metastasis to the pancreas can lead to metastatectomy with improvement in survival in certain types of primary cancers. Furthermore, in patients with more than 1 malignancy, identifying the source of the metastasis is important for further management. To evaluate the role of EUS-FNA in the diagnosis of metastasis to the pancreas. Methods: The study was approved by the institutional review board. Retrospective chart review was conducted to identify all patients suspected to have a metastatic lesion to the pancreas on imaging (CT, MRI, PET) and confirmed on FNA (EUS-FNA or IR-guided biopsy) between 2002 and 2014. Results: A total of 70 patients (median age: 64 years [range: 35-83]; males: 43 [61%]) were found to have metastatic pancreatic lesions. EUS-FNA was performed in 54 patients and detected the pancreatic lesions in all patients with one mild pancreatitis. Among the 54 patients who had an EUS-FNA, 22 patients had multiple lesions, 32 patients had single lesions (head [15], body [9], tail [8]). A 22 G needle was used in 17 patients, and 25 G needle was used in 29 patients, and both needles used in 1 patient (missing information on needle size in 7 patients). A median of 3 passes (range:1-7) were done. Rapid onsite evaluation was performed on all patients for specimen adequacy. Specimens obtained via EUS-FNA were diagnostic in 53/54 patients. Specimens obtained via IR-guided biopsy were diagnostic in 17/19 patients. EUS-FNA was diagnostic in 2 patients who had previously undergone a non-diagnostic IR-guided biopsy. IRguided biopsy was diagnostic in 2 patients who had previously undergone a non-diagnostic EUS-FNA. Thus the accuracy was 98% for EUS-FNA and 89% for IR-guided biopsy. Immunoperoxidase stains were performed and contributory to the diagnosis on 35 patients (26 with a cellblock and 9 with cell smears). Cytomorphologic comparison with the primary tumor was used to make a diagnosis on the other 35 patients (13 with a cellblock and 22 with cell smears). There were 7 patients with more than 1 primary cancer, with diagnosis provided by immunostaining in 6 patients (5 with cellblock and 1 with cellsmear) and cytomorphologic comparison with primary tumors in 1 patient. Conclusion: EUS-FNA has a high diagnostic yield and low complication rate in patients with metastasis to the pancreas. Immunocytochemistry and comparison of the cytomorphology with the primary cancer when possible enable accurate diagnosis especially in patients with more than one primary cancer.