[A rare synchronous occurrence of multiple myeloma and pulmonary adenocarcinoma with multiple solitary extramedullary plasmacytomas of the liver].

We report the case of a 62-year-old woman with multiple liver tumors. She was diagnosed with synchronous occurrence of multiple myeloma (MM) and primary pulmonary adenocarcinoma 4 years ago. She was treated with bortezomib and dexamethasone for MM, and then she underwent thoracoscopic lobectomy. After the surgery, she received autologous peripheral blood stem cell transplantation. However, recurrence of MM was observed 9 months later. She received multiple chemotherapies for MM, but the effect was limited. Meanwhile, brain metastasis of pulmonary adenocarcinoma was observed; therefore, she underwent surgical resection and received radiation therapy. Furthermore, she had elevated levels of liver enzymes, and ultrasonography revealed multiple liver tumors. Because of thrombocytopenia, liver biopsy could not be performed, and chemotherapies for MM did not improve the tumors. Therefore, we clinically determined that the liver tumors were metastatic pulmonary adenocarcinomas. The epidermal growth factor receptor mutation was present in the pulmonary adenocarcinoma, so gefitinib was administered. However, the tumors were uncontrollable and the patient died within 1 month. From autopsy, the liver lesion was confirmed to be MM. Synchronous occurrence of MM and other primary cancers is very rare, and no standard treatment has yet been established. Thus, it is crucial to accumulate synchronous cases and develop treatment methods in the future.