What's causing this thing? What's going on as it grows?

               

From http://livewithoutreservations.com/2013/03/16/pancreatic-cancer-and-you/pancreatic-cancer-explainer/

                Surprise!!! It’s all but super impossible to tell exactly what causes pancreatic cancer. Many studies have been done to explain possible risk factors and some causes but it’s very hard to pinpoint why someone may have developed the disease. Studies have shown the cancer is often linked to a genetic mutation in the DNA. This mutation is linked to 3 things: genetics (thanks mom and dad! I thought you loved me!!), behavior (those cigarettes are totally worth it, right?) and, the best reason of all, just because (you pissed off your body somehow and it yelled “you’re not my mom! Let me live my life and stop oppressing me! Stop holding me back from my true potential! I am going to grow out of control now).  So, the prize for major cause goes to “Genetic Mutation”. (Seriously "genetic mutation" don't you have enough awards for causing problems? What are you trying to prove?)

               Now, how does it progress? Well, based on the fact that most people don’t even know they have it until it’s in a much later stage, we can guess that it progresses smoothly and unadventurously. There really isn’t any change going on while the cancer is growing. People feel cold symptoms (sometimes) and fatigue perhaps. They also often have annoying back pain as the tumor invades valuable space where nerves once had room to be free and not pinched and annoyed by this growing brute. Patients just don't experience anything really out of the “ordinary” for anyone who works or goes to school, or has kids, or a dog or essentially is just "alive". At first, pancreatic cancer often feels like being alive, 

               Slight explanation of the most common pancreatic tumor -

“Adenocarcinomas (most common) - Just as the normal exocrine cells of the pancreas do, adenocarcinomas form microscopic glands (collections of cells surrounding an empty space). Adenocarcinomas can grow large enough to invade nerves which can cause back pain. They also frequently spread (metastasize) to the liver or lymph nodes. If this happens the tumor may be considered unresectable.” From this site about pancreatic cancer*

Adenocarcinoma: This is a gland-forming (it makes tubes) cancer.
In this example, the adenocarinoma has wrapped around a nerve (center of the image).*

*What are pancreatic tumors. (2012, November 2). Retrieved April 19, 2015, from http://pathology.jhu.edu/pc/BasicTypes2.php?area=ba