Table 2.

Risk stratification of primary gastrointestinal stromal tumors for aggressive behavior based on tumor size, site, and mitotic index [24].

Tumor parameters		Risk for progressive disease (%), based on site of origin
Mitotic rate	Size	Stomach	Jejunum/Ileum	Duodenum	Rectum
≤5 per 50 HPF
	≤2 cm	None (0%)	None (0%)	None (0%)	None (0%)
	>2, ≤5 cm	Very low (1.9%)	Low (4.3%)	Low (8.3%)	Low (8.5%)
	>5, ≤10 cm	Low (3.6%)	Moderate (24%)	Insufficient data	Insufficient data
	>10 cm	Moderate (10%)	High (52%)	High (34%)	High (57%)
>5 per 50 HPF
	≤2 cm	None	High	Insufficient data	High (54%)
	>2, ≤5 cm	Moderate (16%)	High (73%)	High (50%)	High (52%)
	>5, ≤10 cm	High (55%)	High (85%)	Insufficient data	Insufficient data
	>10 cm	High (86%)	High (90%)	High (86%)	High (71%)

HPF: high-power field.