Can a teenager get pancreatic cancer with no known risk factors and is other wise healthy?

Very rare, but yes. It is a very rare occurrence in the pediatric population. For more info: see, http://www.Cancer.Gov/cancertopics/pdq/treatment/unusual-cancers-childhood/healthprofessional/page4#section_62.
Very uncommon but... Pancreas cancer tends to be a disease of older adults, is highly fatal, associated with smoking, and often has no signs of disease until very late. However, there are rare examples of very young women who get a rare version known as pancreatic neuroendocrine tumors. This is a very different disease and not as lethal as the standard kind w better treatments. Read here http://1.Usa.Gov/vf3idj.