A 42-year-old woman admitted to our hospital because of superior vena cava syndrome in February, 1984, when she was pointed out of mediastinal tumor shadow in a chest X-ray film and M-component of IgG kappa type in serum. Neither bone marrow nor systemic X-ray bone survey revealed the evidence of myelomatosis. For both diagnosis and therapeutic purpose, the mediastinal tumor was surgically removed after irradiation and was examined histlogically. A diagnosis of extramedullary plasmacytoma (IgG κ) was made.
In December, 1984, a local recurrence occurred in the retroperitoneum. The patient has received chemotherapy (MPPO therapy). The tumor promptly subsided following chemotherapy, the M-component disappeared from serum, and tumor turned undetectable from the retroperitoneum. Neither M-component nor tumor has reappeared during 13 months after the first chemotherapy. During the whole course of the disease, there were no plasmocytosis in the bone marrow and no osteolytic lesions.
