The patient presented in this paper was admitted to the hospital for the evaluation of radiologically revealed shadow in both lungs. In the course of diagnostic procedures, fine needle aspiration biopsy of the intrathoracic mass was performed. Cytologic analysis of the smear was performed because of clinical suspicion of plasma cell proliferative disease that was confirmed by bone marrow aspiration. Thus, the cytologic finding of intrathoracic lesion preceded the diagnosis of multiple myeloma.