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 (PDGFR[alpha]) 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 PDGFR[alpha] gene in five. The average sizes of the GIST were 8.7 cm, 5.4 cm and 5.9 cm for KIT gene-mutated, PDGFR[alpha] 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 [greater than or equal to] 5 x 50 highpower fields (HPFs) underwent KIT gene mutations. Conversely, PDGFR[alpha] mutations were observed only in gastric GISTs with a mitotic rate [less than or equal to] 5 x 50 HPFs. By stratifying GISTs according to classes of risk, KIT mutation was shown in most of the high-risk tumours. PDGFR[alpha] 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. S Afr J Surg 2016;54(1)