Table 2.

Anatomic distribution, frequency and treatment response of the most common GISTs groups.

Genetic Type		Frequency	Anatomic Location	Treatment
KIT mutations
Exon 8		<0.1%
Exon 9		6%	small & large bowel	Imatinib sensitiv (800 mg/d)
Exon 11		66%	all locations	Imatinib sensitive
Exon 13		1%	all locations	usually secondary mutation resistant to imatinib, responds to sunitinib
Exon 17		<1%	all locations	secondary mutation resistant to imatinib and sunitinib; have been shown to respond to other TKI like regorafenib
PDGFRA mutations
Exon 12		1%	all locations
Exon 14		<1%	stomach	Imatinib sensitiv
Exon 18 D842V		6%	stomach	Imatinib/sunitinib resistant; good respons to avapritinib
Exon 18 others		1%	all locations	response to imatinib reported
KIT/PDGFRA “wild-type”				Limited responses to imatinib Possible response to other TKIs (limited data)
SDHB IHC+/SDH-competent	NF1 mutation (assoc. with RD)	<1%	small bowel
	NRAS/HRAS/KRAS mutations	<1%	all locations (limited data)
	BRAF mutation	1%	most commonly stomach
	Other rare mutations/fusions		all locations (limited data)
SDHB IHC−/SDH-deficient	SDHA/B/C/D mutations (CSS)	2%	stomach
	Part of the CT *	1%	stomach
	SDHA mutation (young adults)		stomach
	Sporadic pediatric wt- GIST	1%	stomach

Legend: CSS: Carney–Stratakis Syndrome; CT: Carney triad; *: most cases show promotor hypermethylation.