In metachronous cases, the median time interval between GIST and second tumor was 21.5 months.The high frequency of second tumors suggests that an unknown common molecular mechanism might play a role, but it is not likely that KRAS is involved in this common pathogenesis.
The molecular biology of these GIST, originally defined as KIT/PDGFRA wild-type (WT), is complex due to the existence of different subgroups with distinct molecular hallmarks, including defects in the succinate dehydrogenase (SDH) complex and mutations of neurofibromatosis type 1 (NF1), BRAF, or KRAS genes (RAS-pathway or RAS-P).In this extremely heterogeneous landscape, the clinical profile and molecular abnormalities of the small subgroup of WT GIST suitably referred to as quadruple wild-type GIST (quadrupleWT or KITWT/PDGFRAWT/SDHWT/RAS-PWT) remains undefined.
The final section will discuss the 4 most mature examples in the GI tract: (1) HER2 testing to select patients with advanced gastroesophageal adenocarcinoma for anti-HER2 therapy, (2) KIT and PDGFRA mutation analysis to direct tyrosine kinase inhibitor therapy in gastrointestinal stromal tumor, (3) DNA mismatch repair function testing to determine the applicability of adjuvant chemotherapy in patients with stage II colorectal cancer (CRC), and (4) KRAS mutation analysis and related testing to determine the appropriateness of anti-EGFR monoclonal antibody therapy in patients with metastatic CRC.
We studied 14 GISTs (mean size, 2.7 cm) from six men and one woman (mean age, 70 years) applying morphological features and direct sequencing of KIT, PDGFRA, BRAF, and KRAS.