For other researchers the classification of ovarian cancers into just two types is artificial and limits the progress in understanding the biology of the disease: they have proposed 5 clinically, morphologically, and molecularly different classes of the disease, basing on different molecular abnormalities (high-grade serous: BRCA, p53; low-grade serous: BRAF, KRAS; mucinous: KRAS, HER2; endometrioid: PTEN, ARID1A; and clear-cell: HNF1, ARID1A) [33]. This evidence concerns the gene KRAS and ovarian cancer.