摘要
Pancreatic ductal adenocarcinoma (PDA) is the fourth leading cause of cancer-related death and has a poor prognosis with a 5-year survival rate of 9%. In 2019, 56,770 new PDAs and 45,750 deaths are projected to occur in the United States (1). Because of the dismal prognosis, it is important to predict the course of the disease precisely. The TNM staging system is a widely used not only for predicting prognosis but also for collecting and exchanging cancer information. The American Joint Committee on Cancer (AJCC) Cancer Staging Manual, 8th edition was introduced in October 2016 and there were many changes in the staging of PDA compared with the previous one. Of the several controversies related with the previous edition, the most important one was the reproducibility of the T-category. In the 7th edition, there were discrepancies in opinion among pathologists about pT3 (extension beyond the pancreas). Because the pancreas does not have a capsule, it is difficult to determine if there is an extra-pancreatic extension in the presence of inflammation or desmoplasia. Therefore, in the revised staging system, T-category was classified by size, regardless of the extra-pancreatic invasion: pT1, ≤2 cm in maximal diameter;pT2,>2 cm but ≤4 cm;pT3, >4 cm;pT4, locally unresectable due to involvement of major arteries (the celiac axis or the superior mesenteric artery). Another controversy in the 7th edition was that the N-category is simply divided into pN0 and pN1. It has been suggested that the N-category should be subdivided because the number of metastatic lymph nodes (LNs) affects prognosis (2).
