Extramedullary plasmacytoma with associated multiple myeloma as a presentation of the posterior mediastinal mass: a rare clinical encounter.

A plasmacytoma is a single, isolated tumour of abnormal plasma cells. It can develop within the bone, known as solitary plasmacytoma of bone, or outside the bone, referred to as extraosseous (extramedullary) plasmacytoma, without spreading to other parts of the body. Plasmacytoma, an uncommon presentation in the posterior mediastinum, usually arises as solitary or multiple lesions in bone or soft tissues. The standard treatment involves definitive radiotherapy, potentially curative for extramedullary cases. The prognosis varies, being more favourable without concurrent multiple myeloma and worsening with high-risk cytogenetics. The case involves a male in his early 80s with an extensive medical history presenting with difficulty swallowing and dyspnoea. The diagnosis revealed a rare posterior mediastinal plasmacytoma associated with multiple myeloma, emphasising the importance of prompt diagnosis and treatment.