Abstract
Thymomas are the most frequent adult mediastinal cancers. Their etiology is unknown and their pathogenesis poorly understood. Racial, ethnic and environmental factors influence tumorigenesis in many cancers, but their role in thymomas remains unclear to date. In this study that included pretreatment thymoma cases from India and Germany (n = 37 and n = 77, respectively) we compared i) the prevalence of the thymoma-specific chromosome 7 c.74146970T > A mutation of the GTF2I gene in type A and AB thymomas; ii) epidemiological features; and iii) the frequency of myasthenia gravis (MG). Due to a known predominance of GTF2I mutation in A and AB histotypes, we included only a marginal number of type B thymomas as a control group in both cohorts. While the distribution of histological types between the cohorts was similar (p = 0.1622), Indian patients were strikingly younger (p < 0.0001; median age 50 vs. 65 years) and showed significantly lower tumour stage (Masaoka-Koga stage I) at primary diagnosis (p = 0.0005) than the German patients. In patients with known MG status (n = 17 in Indian and n = 25 in German cohort), a clear trend towards more frequent MG was observed in the Indian group (p = 0.0504; 48 vs. 82%). The prevalence of the GTF2I mutation (analysed in n = 34 Indian and n = 77 German patients) was identical in the two cohorts. We conclude that racial-ethnic and environmental factors do not significantly influence the most common molecular feature of thymomas but may have an impact on the timing of clinical presentation.
Highlights
Thymic epithelial tumours (TET)are the most common tumours arising in the anterior mediastinum in adults, comprising mainly thymomas and the rarer and more aggressive thymic carcinomas [1]
The focus here is on thymomas that are subdivided into type A, AB, B1, B2, and B3 and rare other subtypes according to histological criteria of the WHO classification
Among various other genomic alterations, the most common one is the point mutation in chromosome 7 c.74146970T > A of the general transcription factor II-I (GTF2I) gene that has been identified to be specific to thymic epithelial tumours, predominantly in type A and AB thymomas and associated with a more favourable prognosis[7, 8]
Summary
Thymic epithelial tumours (TET)are the most common tumours arising in the anterior mediastinum in adults, comprising mainly thymomas and the rarer and more aggressive thymic carcinomas [1]. Since the mutation has not been widely studied with respect to different racial and ethnic backgrounds, we aimed to identify its prevalence in two populations from different regions of the world and identify any geographical variability if present in the molecular profile of thymomas. With this objective in mind, we carried out a retrospective analysis, to assess the frequency of GTF2I mutation in Indian and German thymomas (mainly type A and AB) and to correlate it with clinical features
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