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Unique correlation between GTF2I mutation and spindle cell morphology in thymomas (type A and AB thymomas)
  1. Kirsty Wells1,2,
  2. Angela Lamrca3,
  3. George Papaxoinis4,
  4. Andrew Wallace5,
  5. Anne Marie Quinn6,
  6. Yvonne Summers3,
  7. Daisuke Nonaka7
  1. 1Genomic Diagnostic Laboratory, Manchester Centre for Genomic Medicine, Manchester, UK
  2. 2Blueprint Genetics, Helsinki, Finland
  3. 3Medical Oncology, The Christie NHS Foundation Trust, Manchester, Manchester, UK
  4. 4Department of Medical Oncology, Agios Savvas Anticancer Hospital, Athens, Greece
  5. 5Manchester Centre for Genomic Medicine, Manchester University NHS Foundation Trust, Manchester, UK
  6. 6Histopathology, Galway University Hospitals, Galway, Ireland
  7. 7Cellular Pathology, Guy's and St Thomas' Hospitals NHS Trust, London, UK
  1. Correspondence to Dr Daisuke Nonaka, Cellular Pathology, Guy's and St Thomas' Hospitals NHS Trust, London, UK; DNonaka{at}msn.com

Abstract

Aim Recent study has revealed frequent GTF2I mutation in thymomas, with the frequency being highest in types A and AB, followed by B1, B2, B3 and thymic carcinoma. This has led to the conclusion that GTF2I mutation correlates with more indolent histology subtype and better prognosis. In our study, the GTF2I mutation was tested in thymic epithelial tumours to investigate the relation between the mutation status and histology subtype.

Methods The GTF2I mutation was tested in 111 thymic epithelial tumours by Sanger sequencing. Correlations between GTF2I mutation status and clinicopathological parameters were evaluated.

Results There were 16 cases of type A, including atypical type, 37 type AB, 13 B1, 23 B2, 9 B3, 6 micronodular type, 2 metaplastic type and 5 thymic carcinomas. GTF2I mutation was seen in 78.6% of type A and 83.9% of type AB, while it was not expressed in type B, metaplastic type or thymic carcinoma (p<0.001). 75% of micronodular type also showed the mutation. Both thymoma histotype and stage were significantly associated with GTF2I mutation by univariate analysis. The presence of GTF2I mutation showed a trend towards a favourable prognosis, but this is likely due to their strong association with more indolent histologic subtypes (types A and AB).

Conclusions GTF2I mutation appears unique in type A and AB thymomas, including those with atypical features and micronodular type, all of which share spindle cell morphology, indicating they represent a group biologically distinct from type B thymomas.

  • pathology
  • surgical
  • molecular biology
  • neoplasms

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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Footnotes

  • Handling editor Runjan Chetty.

  • Contributors KW, AW, AMQ and YS: Practical experiments. AL: Data collection. GP: Data analysis and manuscript writing. DN: Practical experiments, data collection, data analysis, manuscript writing and guarantor.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.