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Background: Majority of gastrointestinal stromal tumours (GISTs) are characterised by KIT-immunopositivity and the presence of KIT/platelet-derived growth factor receptor alpha (PDGFRA) activating mutations. Patients and methods: Spectrum and frequency of KIT and PDGFRA mutations were investigated in 427 GISTs. Univariate and multivariate analysis of relapse-free survival (RFS) was conducted in relation to tumours' clinicopathologic features and genotype. Results: Mutations were found in 351 (82.2%) cases, including 296 (69.3%) KIT and 55 (12.9%) PDGFRA isoforms. Univariate analysis revealed higher 5-year RFS rate in women (37.9%; P = 0.028) and in patients with gastric tumours (46.3%; P < 0.001). In addition a better 5-year RFS correlated with smaller tumour size ≤5 cm (62.7%; P < 0.001), tumours with mitotic index ≤5/50 high-power fields (60%; P < 0.001), and characterised by (very) low/moderate risk (70.2%; P = 0.006). Patients with GISTs bearing deletions encompassing KIT codons 557/558 had worse 5-year RFS rate (23.8%) than those with any other KIT exon 11 mutations (41.8%; P < 0.001) or deletions not involving codons 557/558 (33.3%; P = 0.007). Better 5-year RFS characterised patients with KIT exon 11 point mutations (50.7%) or duplications (40%). By multivariate analysis, tumours with PDGFRA mutations and KIT exon 11 point mutations/other than 557/558 deletions had lower risk of progression than with KIT exon 11 557/558 deletions (both Ps = 0.001). Conclusions: KIT/PDGFRA mutational status has prognostic significance for patients' outcome and may help in management of patients with GISTs. [ABSTRACT FROM PUBLISHER]

Abstract: Cytogenetic analysis was performed of six monophasic synovial sarcomas (four primary, two recurrent tumors) and one recurrent poorly differentiated synovial sarcoma with complex tumor-specific t(X;18). In the complex translocations, besides chromosomes X and 18, the following chromosomes were involved: 1, 3, 5, 15, and 17. In all, taking these results together with findings of 20 previously published synovial sarcoma tumors with complex t(X;18), 13 different chromosomes were involved. Chromosomes 15 (22% of tumors) and 1, 5, and 12 (∼11% each) were the most frequently involved in complex translocation, but with different breakpoints. In our laboratories, complex tumor-specific t(X;18) ranged from 2.5% to 11.7% (average 6.5%) of synovial sarcoma karyotypes. [Copyright &y& Elsevier]