Table II.

Fuhrman and ISUP grading systems.

Fuhrman grading system	ISUP grading system
Grade 1	Grade 1
Tumors were composed of cells with small (~10 µm) round uniform nuclei with inconspicuous or absent nucleoli	Nucleoli are inconspicuous or absent at a magnification of ×400
Grade 2	Grade 2
Tumor cells had larger (~15 µm) nuclei that exhibited irregularities in the outline and nucleoli when examined under high-power magnification (×400)	Nucleoli are clearly visible at high-power magnification, but are not prominent
Grade 3	Grade 3
Tumor cells had even larger nuclei (~20 µm) with an obviously irregular outline and prominent large nucleoli even at low-power magnification (×100)	Nucleoli are prominent and are easily visualized at low-power magnification
Grade 4	Grade 4
Tumor cells exhibit characteristics similar to those of grade 3 tumors with the addition of bizarre, often multilobed nuclei and heavy chromatin clumps. These tumors often display areas of spindled-shaped cells resembling sarcomas	Presence of tumor giant cells and/or marked nuclear pleomorphism and/or with rhabdoid or sarcomatoid differentiation

ISUP, International Society of Urological Pathology.