TABLE 1.

Overview of the Armed Forces Institute of Pathology¹⁹ Criteria for Risk Assessment in Gastrointestinal Stromal Tumor

Tumor Group	Tumor Size (cm)	Tumor Mitotic Rate (per 50 HPFs)	Risk of Progressive Disease (%)*
			Gastric GISTs	Jejunal and Ileal GISTs	Duodenal GISTs	Rectal GISTs
1	≤ 2	≤ 5	0 (none)	0 (none)	0 (none)	0 (none)
2	> 2 to ≤ 5	≤ 5	1.9 (very low)	4.3 (low)	8.3 (low)	8.5 (low)
3a	> 5 to ≤ 10	≤ 5	3.6 (low)	25 (moderate)	34 (high**)	57† (high**)
3b	> 10	≤ 5	12 (moderate)	52 (high)
4	≤ 2	> 5	0†	50†	‡	54 (high)
5	> 2 to ≤ 5	> 5	16 (moderate)	73 (high)	50 (high)	52 (high)
6a	> 5 to ≤ 10	> 5	55 (high)	85 (high)	86 (high**)	71 (high**)
6b	>10	> 5	86 (high)	90 (high)

Abbreviations: HPF, high-power field; GIST, gastrointestinal stromal tumor.

^*GIST data are presented for patients with progressive disease during long-term follow-up and characterization of risk for metastasis.

^**Combined groups because of the small number of cases.

^†Small number of cases.

^‡No tumors of such category included.