Extramedullary Plasmacytoma of the Lung – Rather a Disseminated than a Localized Disease? – A Case Report of a Primary Pulmonary Plasmacytoma Showing Distinct Signs of Systemic Spread

Objective: We report an unusual case of a patient with a plasma cell tumor presenting first as a primary pulmonary plasmacytoma (PPP) but then showing distinct signs of systemic spread. Case Summary: A 58-year-old woman presented with an extramedullary plasma cell tumor of the lung with additional affection of lymph nodes above and underneath the diaphragm, without apparent infiltration of the bone marrow by malignant plasma cells, but with evidence of a small proportion of clonal plasma cells in FACS analysis. Due to the fact that the patient showed excretion of lambda light chains in the urine in addition to the solid manifestations on multiple sites and minimal bone marrow involvement, we verified the systemic spread. This is in contrast to primary extramedullary plasmacytoma presenting as solitaire plasma cell tumors mostly occurring in the upper aerodigestive tract or extramedullary myeloma, which describes relapses or extramedullary progression of multiple myeloma emerging in various organs. We herein present all features of a, to our opinion, systemic disease by means of affection pattern, laboratory values, and bone marrow infiltration. Conclusion: This unusual case demonstrates the presentation of an extramedullary plasma cell tumor that appeared as a PPP but showed distinct signs of dissemination as well as uncommon features such as a monoclonal component of IgM type. This example reveales that extramedullary manifestations of plasma cell dyscrasia should be surveyed carefully as they can conceal an underlying systemic disease.