Hematologic malignancies often involve the pancreas, causing potential diagnostic pitfalls and, rarely, potentially avoidable surgical resection. We review the spectrum of hematologic malignancies involving the pancreas and describe features useful in preoperative distinction from adenocarcinoma. Archived clinical, pathologic, and radiologic data (1965 to present) for hematologic malignancies involving the pancreas were reviewed and compared with the data for 157 surgically resected pancreatic adenocarcinomas. Of 42 cases, 27 (64%) were clinically "suspicious" for hematologic malignancies. Of the remaining 15 cases, 4 patients underwent resection for presumed pancreatic adenocarcinoma. Isolated pancreatic masses proved most difficult to identify clinically. Significant factors in distinguishing hematologic malignancies from adenocarcinoma included history of hematologic malignancy, young age, large tumor size, low CA19-9 level, B symptoms, and lack of jaundice or diabetes mellitus. Various hematologic malignancies involve the pancreas, most commonly diffuse large B-cell lymphoma. Pancreatic masses are usually correctly identified clinically. Preoperative and operative sampling is strongly recommended when hematologic malignancies cannot be excluded.