The human embryo begins life with two ducts in the pancreas, the ventral duct, and the dorsal duct. Normally, the two ducts will fuse together to form one main pancreatic duct; this occurs in more than 90% of embryos. In approximately 10% of embryos the ventral and dorsal ducts fail to fuse together, resulting in pancreas divisum.
In general, there are two main varieties of pancreatic cysts based on the type of fluid they contain. The most common cysts are either serous (containing a thin type of fluid) or mucinous (containing a thicker, more viscous fluid). For the most part, serous cysts tend to be benign (non-cancerous). Most of the mucinous cysts are benign as well although there are a few subtypes that can be more concerning.