A 68-year-old woman was admitted in March 1997 because of lumbago, fever, vomiting, and general malaise. Laboratory data disclosed anemia and severe hypercalcemia (7.7 mEq/l). Multiple osteolytic lesions were detected in the patient's vertebra, pelvis, and bilateral tibia by x-ray films and 99mTc bone scintigrams. Bone marrow aspiration sample was not obtained due to dry tap. Marked myelofibrosis and proliferation of lymphoid cells were revealed by a bone marrow biopsy specimen. Immunohistochemical analysis showed that cells in the biopsy specimen were positive for L-26 and LCA, but not for UCHL-1. Gastrointestinal endoscopic examination found multiple polypoid lesions in the stomach; biopsy specimens of the lesion tissue disclosed invasion by B lymphoid cells. A diagnosis of diffuse large B cell lymphoma was thus made. THP-COP chemotherapy was performed, but only minimal response was obtained. Lymphoma cells subsequently invaded the brain stem, and the patient eventually died of respiratory failure.