Mutations in KRAS oncogene are an early event in the pathogenesis of ovarian mucinous tumors and are seen in 30%-75% of cases. The image shows mucinous borderline tumor - intestinal type (higher magnification from the previous image). The lining epithelium shows a complex glandular architecture. The glands are arranged back to back, separated by thin stromal cores. The lining epithelium is tall columnar mucinous type with basally located hyperchromatic nuclei lacking cytologic atypia.