A lack of actionable mutations in phyllodes tumours of the breast

Aims Phyllodes tumours (PT) are rare fibro-epithelial lesions of the breast for which clinical behaviour is not reliably predicted by the pathological features. They have an unpredictable risk of recurrence and potential for metastatic spread, with no effective therapies if surgical control is not possible. New therapeutics that target specific mutant tyrosine kinase receptors have been developed and used successfully in a range of malignancies. We assessed 30 PT for the presence of common, actionable mutations using a sensitive, high-throughput mass spectrometry based assay which detects a panel of 238 specific mutations in 19 oncogenes. Methods DNA was extracted from four fibroadenomas (FA), 18 benign (low grade), six borderline and six malignant PT, prepared using the Oncocarta v1.0 kit and processed on the Sequenom compact MassARRAY platform. Results Analysis of four FA and 30 PT revealed that there were no targeted mutations, including within a malignant PT with heter-ologous differentiation, and two recurrent tumours (one borderline and one malignant PT). Conclusions This study highlights the ongoing complexity in understanding the pathogenesis of PT, which lack common, actionable mutations. We are currently undertaking further studies utilising more comprehensive next generation mutation panels on this group of tumours.