. 2011 Jan 21;12(1):773–794. doi: 10.3390/ijms12010773

Table 2.

Grading systems for epithelial ovarian carcinoma: FIGO, universal three tier grading and two tier grading.

Grading system		Grade	Key features			Ref.
FIGO		1	Well differentiated	Grade based on % solid non-squamous growth, grade + 1 if nuclear atypia apparent	<5% solid growth	[10]
		2	Moderately differentiated		6–50% solid growth	[10]
		3	Poorly differentiated		>50% solid growth	[13]
3-tier universal grading		1	Grade based on sum of individual feature scores (see right) 1 = 3–5 points 2 = 6–7 points 3 = 8–9 points	Architecture based score	Glandular = 1 point Papillary = 2 points Solid = 3 points	[13]
		2		Nuclear pleomorphism score	Slight = 1 point Moderate = 2 points Marked = 3 points	[12]
		3		Mitotic activity score	0–9 = 1 point 10–24 = 2 points ≥25 = 3 points	[12]
2-tier grading	Serous tumour	Low grade (type I)	Slow development	Low chromosomal instability	Gene mutation–KRAS, BRAF, ERBB2	[14]
	Serous tumour	High grade (type II)	Rapid development	High chromosomal instability	Gene mutation–P53	[14]
	Endomet roid tumour	Low grade	Well differentiated, no necrosis	Solid glandular architecture	Gene mutation–Wnt, PI3K/Akt	[13]
	Endomet roid tumour	High grade	Solid growth >50%, necrosis	Diffusely infiltrative or expansive growth, no glandular architecture	Gene mutation–TP53	[16]