Morphology of Pancreatic Exocrine Tumors

Abstract

Classification of tumors is important for understanding the tumor histogenesis and prognosis. Since 1836, when pancreatic cancer was first described [1], progress has been made in pancreatic cancer morphology. However, there are still inconsistencies in the description and classification of pancreatic tumors, mostly because of the lack of information on the natural history of the disease. The silent course of the disease and its late clinical manifestation and diagnosis are contributing factors, as are the insufficient availability of tissues (biopsy, autopsy), the technique in preparation of the specimen, methods of histological examination (including the number of sections taken for evaluation), and personal experience. Therefore, some of the classifications have been either simplified, exaggerated by details or are incomplete [2–10]. For example, the classification by Cubilla and Fitzgerald [5] and Sommers and Meissner [10] include mixed duct-islet, duct-islet-acinar and acinar-islet tumors. In our experience and that of others [11–17], more than 70% of pancreatic carcinoma contains endocrine cells, some in a pattern consistent with the mixed-cell tumors of Cubilla and Fitzgerald (Figs. 1, 2). Therefore, Kloppel and Heitz [18] do not classify these tumors as separate entities, and rightly so. The same applies for the mixed acinar-islet and carcinoid-islet cell tumors that neither we nor other investigators have encountered in their material, except for rare tumors that contain both zymogen and endocrine granules [17]. Such tumors should not be regarded as mixed tumors but rather reflect altered differentiation.