Fuhrman Grading System . Grade X (GX): Cannot be assessed . Grade 1 (G1): Nuclei round, uniform, approximately 10 um in diameter; nucleoli inconspicuous or absent . Grade 2 (G2): Nuclei slightly irregular, approximately 15 um in diameter; nucleoli evident . Grade 3 (G3): Nuclei very irregular, approximately 20 um in diameter; nucleoli large and prominent . Grade 4 (G4): Nuclei bizarre and multil..