Malignant mesothelioma typically presents in patients with asbestos exposure, with respiratory symptoms caused by primary pleural involvement with associated pleural effusion. Instead, this patient presented with a rapidly growing posterior mediastinal mass, without a pleural lesion or known asbestos exposure. Common differential diagnosis for posterior mediastinal masses usually indudes neurogenic tumors (accounts for 60%), meningoceles, and spinal lesions. and did not include mesothelioma prior to this encounter (1 ). Repeated pleural fluid analyses and EBUS-FNA tissue samples were insufficient to yield a definitive diagnosis and resulted in delay of diagnosis and subsequently significant growth and progression of the patient's disease. Treatment options remain mostly palliative with prognosis typically less than 12 months, but if detected early, a combination of chemotherapy/ surgery regimens can prolong survival to an average of 22 months (2).