Metastatic tumors to the pancreas: An institutional experience

Metastatic malignancies to pancreas are extremely rare with most common origins being kidney and melanoma. This study aims to evaluate types of solid malignant metastasis in pancreatic FNAs at our institution along with comprehensive review of reported literature. Our laboratory information system was queried over years 2000-2024 to identify all pancreatic FNAs with metastasis. "Positive for Malignant Cells" diagnosis was included in our review. "Atypical" or "Suspicious for malignancy" were excluded. Type of metastatic malignancy, location and presence of synchronous metastasis were documented. Our results show that out of 4051 pancreatic FNAs with "Positive for Malignant Cells", 83 (2 %) cases were metastatic, while remaining 127 cases represented primary pancreatic adenocarcinomas or neuroendocrine tumors. 43 (52 %) renal cell carcinomas, 15 lung carcinomas (17.6 %), 7 skin melanoma (8.2 %),4 breast ductal adenocarcinoma (4.7 %), 3 urothelial carcinomas (3.5 %), 2 leiomyosarcoma (2.4 %), 2 ovarian serous carcinoma (2.4 %),1 uterine adenocarcinoma (1.2 %),1 prostatic carcinoma (1.2 %), 1 skin Merkel-cell carcinoma (1.2 %),1 gastric adenocarcinoma (1.2 %),1 colorectal adenocarcinoma (1.2 %), and 1 vulvar Squamous-cell carcinoma (1.2 %) were identified. Majority (~59 %) of tumors had synchronous presentation. Most common synchronous organs were lungs, liver, and mesenteric lymph nodes. In conclusion, our study demonstrated further support for lung being the second most common primary site of pancreatic metastasis. Renal origin is the most common secondary tumor in our institutional review, followed by combination of lung, breast, and melanoma. Sarcomas can rarely present as pancreatic metastasis, and thorough clinical and histomorphology correlation is warranted. Origin-specific immunostains and molecular testing may help in challenging secondary pancreatic tumors.