Serous cystadenoma can turn into cancer?

Not usually: Serous cystadenoma (sc) of ovary is a common benign (not cancerous) tumor highly unusual to turn into cancer unless it is classified as serous borderline cystadenoma. Sc may also occur in the pancreas, often in the tail end area. It is also benign but can grow quite large and thus can physically push on other near by structures. If you have trouble, consult doc. Good luck.