Guide to diagnosing primary pancreatic lymphoma, B-cell type: immunocytochemistry improves the diagnostic accuracy of endoscopic ultrasonography-guided fine needle aspiration cytology.

Primary pancreatic lymphoma (PPL) is a rare disease with <1%of extranodal non-Hodgkin's lymphoma arising in the pancreas. This report provides immunocytochemical information on PPL that would be valuable for making differential diagnoses between PPL, pancreatic neuroendocine tumor, acinar cell carcinoma, and pancreatic ductal cancer. A 68-year-old woman had a chief complaint of abdominal pain. Fine needle aspiration cytology (FNAC)was performed. The FNAC smear showed moderate cellularity,with a small to moderate number of irregular cells and lymphocytes.No epithelial tumor clusters or abundant mucoid background were seen. The cells were scattered with pleomorphism and showed irregular nuclear shapes with finely granular chromatin,an increased nuclei–cytoplasm ratio, and prominent nucleoli.Cytologically, PPL was suspected with Papanicolaou staining but definite diagnosis was not made. Therefore, the specimen was destained, immunocytochemically examined for leukocyte common antigen (LCA), and PPL was suspected again. Numerous tumor cells were found in the surgical sample and tumor cells were positive for CD20 and negative for CD45RO. Based on these findings,the tumor was diagnosed as PPL, B-cell type. The preoperative FNAC smear that was examined for LCA was then reexamined for CD20, CEA, and Synaptophysin. As a result, the tumor cells were positive for LCA and CD20, whereas they were negative for CEA and Synaptophysin. Taking these findings together with the cytopathologic findings, this specimen was reconfirmed as PPL. Immunocytochemical examination for LCA and CD20 is useful in the identification of malignant pancreatic lymphoma, B-cell type.