Small and microscopically detected gastrointestinal stromal tumours: an overview

Small or microscopic gastrointestinal stromal tumours (GISTs) have been the focus of recent publications. These lesions may accompany clinically overt GISTs or be found incidentally in resection specimens for gastro-oesophageal malignancies. While the majority of cases consist of single lesions, approximately 30% may be multiple (usually two or three such lesions). Several appellations have been employed to describe these small GISTs: minute GISTs, GIST tumourlets, interstitial cell of Cajal (ICC) hyperplasia, microscopic GISTs, minimal GISTs, and sclerosing stromal tumourlets. As such, there has been no uniformity in terms of the size of these small or microscopic lesions with tumours as small as 0.2 mm and those up to 10 mm, all falling within the remit of microscopic or minute GISTs. These lesions have a predilection for the gastro-oesophageal junction and occur slightly more frequently in the proximal stomach. They are typified by spindle-shaped cells set within a hyalinised stroma which also shows calcification. Even the smallest lesion has been shown to harbour mutations of the c-kit gene. They are biologically indolent, and the majority of lesions appear to remain small and/or show evidence of involution. However, it is possible that some are the precursors of clinically significant GISTs.