Most mucinous ovarian carcinomas harbor KRAS mutations (codons 12, 13). This is an early event as identical mutations are also present in the benign and borderline components of the same carcinoma. About 15-20% of cases show HER2 amplification. These cases donít harbor KRAS mutations. The image shows mucinous carcinoma with destructive stromal invasion. The invasive foci are composed of distorted glands, isolated tumor cells, and small nests or clusters of cells with high-grade nuclear features that are haphazardly infiltrating desmoplastic stroma.