Endoscopic ultrasound-guided fine-needle aspiration of metastases to the pancreas: A study of 25 cases

Background: Metastases to the pancreas are an uncommon cause of pancreatic masses seen on endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA). The purpose of this study is to retrospectively review the cytomorphology, clinical findings, and results of ancillary studies in a large series of these unusual cases. Materials and Methods: We searched our institutions pathology database for EUS-guided FNAs of the pancreas that were diagnostic of metastatic tumor over a 5-year period. The final cytologic diagnosis, results of ancillary studies, corresponding histological material, and clinical follow-up data were reviewed in these cases. Results: A total of 1172 pancreatic EUS-guided FNAs were identified, of which 25 cases (2.1) had a confirmed diagnosis of a pancreatic metastasis. This included 12 (48) cases of renal cell carcinoma, 3 (12) melanomas, 3 (12) small cell carcinomas, and 7 (28) other malignancies. In these metastatic tumors involving the pancreas, 20 (80) of the lesions were solitary. Four (16) cases had no prior history of malignancy. The average time to diagnosis of pancreatic metastasis was 5.3 years. Immunohistochemistry and special stains were performed in 22 (88) and 9 (36) cases, respectively. Conclusions: Our data shows that although metastases to the pancreas are rare, they can present as a solitary mass many years after the primary malignancy is diagnosed and can even be the first manifestation of an extrapancreatic primary in a small number of cases. It is important to consider the possibility of a metastatic lesion in the pancreas because this may require a different management than a primary pancreatic tumor.