Primary plasmacytoma of the lung: A case report and review of literature

Solitary extramedullary plasmacytomas are uncommon entities accounting for less than 5% of all plasma cell neoplasms. Primary plasmacytomas of the lung are exceedingly rare, with approximately thirty-six cases described in the modern literature. We describe a case of a primary pulmonary plasmacytoma in a 47-year-old male. A mass within the upper lobe of his right lung was incidentally discovered on computed tomography (CT) and biopsied multiple times over the course of one year with inconclusive results. Due to continued growth of the tumor, a wedge resection of the right upper lobe was performed. Histologically, normal pulmonary alveolar architecture was effaced by a dense infiltrate of inflammatory cells. These cells were predominantly monomorphic and mature plasma cells, staining positive for CD138 and negative for CD20. Kappa and lambda light chain in situ hybridization revealed kappa restriction, with rare scattered lambda positive reactive plasma cells. A diagnosis of primary plasmacytoma of the lung was made, pending workup for any systemic involvement by multiple myeloma. This workup revealed a normal bone marrow biopsy, a bone scan without lytic lesions, and both urine and serum protein electrophoresis devoid of abnormal protein restriction. Approximately six months later, the patient does not have evidence of residual or recurrent disease, and is being closely monitored.