Abstract
Synchronous pleural mesothelioma (PM) and breast cancer are extremely rare. We present the case of a 53-year-old female diagnosed with localized breast cancer. She was radically treated with surgery, but during the adjuvant radiotherapy, the patient developed fever and dyspnoea, and pleural thickening was found on a CT scan. The biopsy confirmed the diagnosis of a synchronous malignancy - pleural epithelioid mesothelioma. The patient stopped radiotherapy and started adjuvant endocrine therapy with exemestane, a third-generation aromatase inhibitor, with an unexpected partial response to the PM. The patient remains on exemestane with a sustained partial response. This is a rare case of synchronous tumours that show a real-life benefit of exemestane in the treatment of pleural mesothelioma, which was only described in vitro, with a good sustained response. This suggests a potential for exemestane in the treatment of mesothelioma, which is an aggressive form of cancer with few therapeutics with sustained results.