Table 1.

Mutations and clinicopathological features

Genes	Exon	Frequent mutations	Frequency	Characteristics and site	Imatinib sensitivity
KIT	All exons		80 %	All sites
	8		Rare	Small bowel	Yes, intermediate
	9	Insertion of AY 502–503	5–10 %	Small bowel, colon, spindle, aggressive
	11	Deletions, missense mutations, insertions	60–70 %	All sites	Yes
		Deletion of codon 557 or 558		Aggressive, poor prognosis
		Internal tandem duplication		Benign features, clinically indolent, female, stomach
	13	K642E	1 %	All sites	Yes
	17	D820Y, N822K, Y823D	1 %	All sites	No for D816V
PDGFRA	All exons		10 %	Epithelioid, clinically indolent
	12	Missense mutations	1–2 %	All sites	Yes
	14	N659K	<1 %	Stomach, epithelioid	Yes
	18	D842V	10–5 %	Stomach, mesentery, omentum, epithelioid	No for D842V
Wild-type			10–15 %	All sites	Probably no
BRAF		V600E	Rare
SDHA/SDHB/SDHC/SDHD mutations			~2 %	Carney–Stratakis syndromea; stomach, multiple, immunohistochemically SDHB negative
				Juvenile GIST; stomach, clinically indolent, multiple, immunohistochemically SDHB negative
Loss of SDH expression				Carney triadb; stomach, clinically indolent, juvenile onset, immunohistochemically SDHB negative
HRAS, NRAS mutation			<1 %
NF1 mutation			1–2 %	Small bowel, clinically indolent, multiple, spindle

SDH succinate dehydrogenase, SDHB succinate dehydrogenase iron–sulfur subunit (subunit B)

^aCarney–Stratakis syndrome: familial syndrome of multiple GIST and paragangliomas with autosomal dominant inheritance and germline mutation in the SDH complex

^bCarney triad: coexistence of gastric gastrointestinal stromal tumor (GIST), pulmonary chondroma, and extra-adrenal paraganglioma in young women, postulated to be defect in expression of the SDH complex