Histological grade of primary tumour according to the AJCC cancer staging manual, seventh edition (2009)19
| G | Number of cases |
| GX | 18 |
| G0 | 0 |
| G1 | 34 |
| G2 | 0 |
| G3 | 94 |
| G4 | 24 |
| Total | 170 |
Springer Science and Business Media (www.springerlink.com, accessed 2 March 2009).
The histological grade represents the origin of the primary tumour. Because this study only included invasive melanoma of the conjunctiva there are no cases of G0 or G2.
G, histological grade; GX, origin cannot be assessed; G0, primary acquired melanosis without cellular atypia; G1, conjunctival nevus; G2, primary acquired melanosis with cellular atypia (epithelial disease only); G3, primary acquired melanosis with epithelial cellular atypia and invasive melanoma; G4, de novo malignant melanoma.