Incidental discovery of multiple myeloma, presenting as an amyloid tumor with plasmacytic elements of the thoracic wall

Multiple myeloma is characterized by monoclonal proliferation of bone marrow plasma cells causing multiple bone lesions and overproduction of a monoclonal protein (M-protein) that could deposit in tissues (amyloidosis). Dissemination of the multiple myeloma outside the bone is rare.

We present a case of a 76 years old woman presenting with dry cough. Chest X-ray showed a giant tumor of the upper right lung. Contrast enhanced CT revealed a tumor that most probably originated from the structures of the thoracic wall. The transthoracic biopsy was inconclusive. The tumor was resected and the histopathological examination showed amyloid tumor of the thoracic wall with plasmacytic elements and lambda light chains deposits. A bone marrow aspiration was performed that found diffuse plasmacytic infiltrate of 20-60% and the serum proteins electrophoresis with immunofixation revealed elevated IgA and lambda light chains. The patient was diagnosed with IgA and lambda light chains multiple myeloma with consequent AL amyloidosis presenting as thoracic mass.