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Henzinger, H.
The Role of Methylation Analysis in Distinguishing Cellular Myxoma from Low-Grade Myxofibrosarcoma
Humanmedizin; [ Diplomarbeit ] Medizinische Universität Graz; 2024. pp.

Authors Med Uni Graz:
Advisor:: Brcic Iva; Liegl-Atzwanger Bernadette
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Abstract:: Cellular myxoma is a benign soft tissue tumor frequently associated with GNAS mutation. It may morphologically resemble low-grade myxofibrosarcoma which, due to the absence of specific immunohistochemical markers in both entities, can cause diagnostic challenges. In recent years, DNA methylation and copy number profiling have been established as alternative tools that can provide valuable additional information for a more accurate classification of different neoplasms. This study aimed to identify the undescribed methylation profile of cellular myxoma and compare it to low grade myxofibrosarcoma. We performed molecular analysis on twenty cellular myxomas and nine myxofibrosarcomas and analyzed the results using the methylation-based DKFZ sarcoma classifier. A total of 90% of the cellular myxomas had GNAS mutations (four loci had not been previously described). Copy number variations were found in all myxofibrosarcomas but in none of the cellular myxomas. In the classifier, none of the cellular myxomas reached the 0.9 threshold required for a valid classification. Unsupervised tSNE analysis demonstrated that cellular myxomas form their own clusters, distinct from myxofibrosarcomas. Our study shows the diagnostic potential, but also the limitations of molecular analysis in cases where morphology and immunohistochemistry are not sufficient to distinguish cellular myxoma from myxofibrosarcoma, particularly regarding GNAS wild-type tumors. The DKFZ sarcoma classifier only provided a valid prediction for one myxofibrosarcoma case; this limitation could be improved by training the tool with a more considerable number of cases. Additionally, the classifier should be introduced to a broader spectrum of mesenchymal neoplasms, including benign tumors like cellular myxoma, whose distinct methylation pattern we demonstrated.