Extramedullary plasmacytoma (EMP) is a plasma cell neoplasm without bone marrow involvement or other systemic characteristics of multiple myeloma. Few large-scale clinical studies have been conducted because of the rarity of EMP. especially when it arises from the mediastinum. Herein we report a rare case of solitary mediastinal plasmacytoma with reactive pleural effusion. https://www.knowall.blog/