Type	Histology	Precursor	Molecular features
I	Low-grade serous carcinoma	Cystadenoma–borderline tumour–carcinoma sequence	Mutations in KRAS and/or BRAF (≥ 60%)
I	Low-grade endometrioid carcinoma	Endometriosis and endometrial cell-like hyperplasia*	Mutations in CTNNB1, PTEN and PIK3CA with microsatellite instability
I	Mucinous carcinoma	Cystadenoma–borderline tumour–carcinoma sequence; metastases from bowel	Mutations in KRAS; TP53 mutation associated with transition from borderline tumour to carcinoma
I	Clear cell carcinoma	Endometriosis	PTEN mutation or loss of heterozygosity; PIK3CA mutation‡
II	High-grade serous carcinoma	De novo in epithelial inclusion cysts; fallopian tube	TP53 mutation (up to 80%) and BRCA1 dysfunction
II	High-grade endometrioid carcinoma	Epithelial inclusion glands or cysts	TP53 mutation and BRCA1 dysfunction; PIK3CA mutation

^*Endometriosis and adjacent low-grade endometrioid carcinoma share common genetic events such as loss of heterozygosity at the same loci involving the same allele (for example, PTEN). By contrast, high-grade and poorly differentiated endometrioid carcinomas are similar to high-grade serous carcinomas.

^‡PIK3CA at 3q26 encodes the p110α catalytic subunit of PI3K¹⁹.