Atypical Presentation of Plasma Cell Neoplasm of the Sternum.

Multiple myeloma (MM) is a rare plasma cell neoplasm characterized by monoclonal cell infiltration in the bone marrow, which can cause anemia, bone pain, and recurrent infections. Extramedullary myeloma (EM) is a rare clinical presentation with a poor prognosis. It involves the accumulation of clonal plasma cells in soft tissues with a tumor-like appearance, either presenting as a primary (initial) or secondary (relapse) malignancy. We present a case of a 65-year-old male who experienced an abrupt onset of chest pain associated with a localized sternal mass while exercising the day prior to arrival. Chest computed tomography (CT) scan with contrast revealed an expansile lytic lesion around the sternal area. Due to high suspicion for malignancy, a CT-guided core needle biopsy was done, which showed plasma cells with rare Dutcher bodies consistent with MM. Bone marrow smear showed the presence of 70% plasma cells confirming a diagnosis of MM. Early detection of this devastating disease may help improve survival. Therefore, physicians should have a high index of suspicion for MM in older patients with similar clinical presentations.