Table 1.

Suggested classification for benign microscopic proliferative ICC lesions/ minute incidenal GISTs

Lesion type/reference	Detection method	Size	Circumscription	Focality	Clinical setting	Common location	Molecular features
ICC hyperplasia, localized type [12,13,17,18]	Microscopic, rarely through careful palpation/inspection	≤5 mm, usually <2 mm	Usually irregular borders, blend with M. propria Rarely diffuse segmental	Usually focal, occasionally multifocal	Sporadic Usually incidental histological findings	Esophagogastric junction (∼10%) Proximal stomach (-35%) Colorectum (0.2%)	Somatic heterozygous mutations in c-KIT (∼25%)
ICC hyperplasia, diffuse type [14-16,26,29]	Microscopic, rarely thickening of M. propria	Variable, commonly confluent	Diffuse to nodular, Usually both	Usually multifocal or continuous	Hereditary Rarely congenital with neuronal intestinal dysplasia (very rare Carney triad)	Variable, any part of GI tract. In NF-1 mostly in small bowel	Germline c-KIT/PDGFRA mutations NF-1 (wild-type KIT/PDGFRA)
GIST tumorlets [30,31]	Grossly visible or palpable	5-10 mm	Usually irregular borders, blending with M. propria	∼10% multifocal	Usually sporadic	Proximal stomach, rarely others	Rarely sporadic c-KIT mutations
Incidental benign GIST [2,23,24]	Grossly visible or palpable	>10-20 mm	Well circumscribed but nonencapsulated	Rarely multifocal	Usually sporadic	Variable, usually proximal stomach, occasionally small bowel and others	Commonly somatic heterozygous mutations in c-KIT or PDGFRA (∼90%)