The bone marrow in multiple myeloma: correlation of plasma cell ultrastructure and clinical state.

The bone marrow plasma cells of 52 patients with various kinds of monoclonal gammopathies were studied by electron microscopy, and compared to the bone marrow plasma cells of 22 patients with reactive plasmacytosis. Virtually every marrow from patients with myeloma and macroglobulinemia contained plasma cells with disparity between the nuclear maturation and cytoplasmic differentiation. This asynchronous development was not present in plasma cells of reactive marrows nor in plasma cells from patients with megaloblastic anemias. The degree of asynchrony observed in myeloma and macroglobulinemia was proportional to the extent of disease as judged by clinical criteria. For the most part plasma cells of patients with non-myelomatous monoclonal gammopathy failed to exhibit significant asynchrony. These observations are consistent with the view that multiple myeloma is a neoplastic disorder with a definably malignant-appearing cellular proliferation.