A voluminous mass as an initial clinical symptom of multiple myeloma: A case report.

Extramedullary multiple myeloma (EMM) is a type of multiple myeloma (MM) that is defined by the presence of extraskeletal (soft tissue or visceral) clonal plasma cell infiltrates, which may be present at the time of initial diagnosis or at the time of relapse. Although extramedullary lesions may be present with other clinical features at the time of diagnosis, the onset of a solid formation as a first clinical symptom of MM is unusual. The present study reports the case of a 77-year-old male who was admitted to the Hematology Unit of the National Cancer Research Center, Istituto Tumori 'Giovanni Paolo II' (Bari, Italy) with a mass protruding from the right side of his lower back. Serum immunofixation revealed positivity for monoclonal protein (M-protein) and Bence Jones proteinuria was positive. In addition, a computed tomography scan of the abdomen, which was confirmed by magnetic resonance imaging, revealed a voluminous solid formation resembling a sarcoma. M-protein is known to be present in numerous diseases encountered in clinical practice, including hematological or other diseases; thus, a Tru-Cut biopsy of the lesion was performed, which revealed an infiltration of plasma cells. In addition, a bone marrow biopsy revealed the presence of 70% plasma cells, and a diagnosis of primary EMM was established. In conclusion, EMM should be included in the differential diagnosis of a mass, particularly in patients where M-protein is detected in the blood and/or urine.