Gastrointestinal stromal tumors

Abstract

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor of the gastrointestinal tract. Soon after GIST was recognized as a tumor driven by a KIT or platelet-derived growth factor receptor mutation, it became the first solid tumor target for tyrosine kinase inhibitor therapies. More recently, alternative molecular mechanisms for GIST pathogenesis have been discovered. These are related to deficiencies in the succinate dehydrogenase complex, NF1-gene alterations in connection with neurofibromatosis type 1 tumor syndrome, and mutational activation of the BRAF oncogene in very rare cases.

Fig. 1

A,B, Gross features of a gastric GIST showing multinodular submucosal masses and a small intestinal GIST showing a fistula tract connecting the center of the tumor to the intestinal lumen.

Fig 2

Wide spectrum of histologic features of gastric GIST. A. Paucicellular tumor with sclerosing matrix. B. Perinuclear vacuolization and nuclear palisading. C. Epithelioid cytology. D. Sarcomatoid appearance with numerous mitoses.

Fig. 3

Histology of small intestinal GIST. A. Spindle cell tumor with extracellular collagen globules. B. Anuclear zones reflecting prominent entangled cell processes.

Fig 4

A, B. Succinate dehydrogenase deficient GIST shows epithelioid cell morphology and shows loss of SDHB, which is only present in non-neoplastic vascular and stromal components. C,D. A conventional GIST in comparison shows granular cytoplasmic staining for SDHB.