KRAS and cystadenoma: Regardless of the origin of ovarian mucinous carcinoma, morphological transitions from cystadenoma to a mucinous borderline tumor (MBT) to intraepithelial carcinoma and invasive carcinoma have been recognized for some time, and an increasing frequency of KRAS mutations at codons 12 and 13 has been reported in cystadenomas, MBTs and mucinous carcinomas, respectively [63–66].