Localised intrapulmonary plasmacytoma represents less than 5% of all extramedullary plasmacytomas. Their diagnosis is usually made difficult by a radiological presentation and non specific endoscopic findings as well as non contributory biochemical and cytological data. This often justifies the recourse to more invasive histological investigation aided by immunohistochemical techniques. We report the case of a patient who presented with an isolated plasmacytoma in the form of two parenchymatous pulmonary masses and who was treated by a combination of surgical resection and external radiotherapy. A search for multiple intraosseous myeloma remained negative. Unfortunately a relapse in the form of mediastinal invasion occurred 6 months after the completion of treatment and led to the death of the patient.