Simultaneous occurrence of T-cell and B-cell neoplasms is rare, and etiologic relationships between these 2 malignancies are poorly understood. We describe the case of a 66-year-old woman who was admitted to the hospital because of fever, hemoptysis, lymphadenopathy, and skin rash. Enlarged lymph nodes in axillary, pectoral, paratracheal, and periportal regions as well as slight hepatomegaly and splenomegaly were confirmed. A peripheral blood smear revealed rouleaux formation and numerous circulating plasma cells, with plasmacytoid lymphocytes. Immunofixation-electrophoresis detected a monoclonal band defined as immunoglobulin (IgG)-lambda light chains with broad-band polyclonal IgA. The patient died from abrupt splenic rupture before diagnostic work-up was finished. Postmortem examination revealed infiltration of atypical lymphoid cells exhibiting high proliferative activity admixed with typical and atypical plasma cells in several organs. Thus, plasma cell leukemia (IgG-lambda) as a rare and aggressive variant of plasma cell myeloma in the present case was associated with aggressive peripheral T-cell lymphoma and polyclonal (IgA) plasmacytosis.