When my uncle was diagnosed with stage 2 pancreatic cancer, I became very interested in what its progression is like. What I found is that stage 0 is the earliest
stage, in which the tumor is confined to the top layers of pancreatic duct cells and has not invaded deeper tissues or spread outside of the pancreas. Only 7% of patients are diagnosed that early.
Stage 1 comes next, and it means that the cancer has formed but hasn't spread beyond the pancreas to nearby lymph nodes or distant sites. Stage I is divided into stage IA and stage IB, based on the size of the tumor. In stage 1A the tumor is 2 cm or smaller. In stage 1B the tumor is larger than 2 cm.
Stage 2 is also divided in to A and B. Stage 2A means that the tumor is growing outside the pancreas but not into large blood vessels and it hasn't spread to nearby lymph nodes or distant sites. Stage 2B means the tumor is in or outside the pancreas, it isn't growing into large blood vessels or major nerves, it hasn't spread to distant sites, but it has spread to nearby lymph nodes.
Actually, rather than typing all this information out, I'm going to refer you to my source. The American Cancer Society web site spells out the specifics of each of the stages in the progression of pancreatic cancer here.