Molecular genetic features and risk assessment in a series of 30 patients who underwent an operation for gastrointestinal stromal tumours

Background: The objective of the study was to investigate the relationship between molecular genetic features and the standard criteria of risk assessment in patients affected by gastrointestinal stromal tumours (GISTs). Methods: A review was conducted of a series of 30 patients, with a mean age of 67 years, who underwent surgery for primary GISTs. R0 resection was accomplished in 27 patients. CD117, CD34 desmin, vimentin, S-100 and smooth muscle actin were immunohistochemically tested to achieve a diagnosis of GIST. The loss of wild-type KIT or platelet-derived growth factor receptor alpha (PDGFRα) genes was investigated by sequencing the tumour DNA. Results: Tumour genes mutations were reported in 23 patients (77%), and wild-type in seven. Mutations on the KIT gene occurred in 18 patients, and mutations on the PDGFRα gene in five. The average sizes of the GIST were 8.7 cm, 5.4 cm and 5.9 cm for KIT gene-mutated, PDGFRα gene-mutated and wild-type tumours, respectively. KIT gene mutations were detected in 50% of gastric and in 70% of extragastric GISTs. Moreover, 70% of tumours with a mitotic rate ≥ 5 x 50 highpower fields (HPFs) underwent KIT gene mutations. Conversely, PDGFRα mutations were observed only in gastric GISTs with a mitotic rate ≤ 5 x 50 HPFs. By stratifying GISTs according to classes of risk, KIT mutation was shown in most of the high-risk tumours. PDGFRα mutations occurred exclusively in lower classes of risk. Conclusion: Molecular analysis data might have a role as a prognostic variable in models of risk assessment for patients with GISTs