A bone marrow examination is indicated for all patients suspected of having MM. The number of plasma cells in marrow may vary from 5%-90%. No single plasma cell is diagnostic for MM. Some morphologic variants, however, are seen more frequently in myeloma than under normal conditions. The nucleus of each of the plasma cells in this slide contains a large nucleolus. Normal plasma cells do not have prominent nucleoli, although they may have small ones, which are usually disguised by the nuclear chromatin. In attempting to make a diagnosis of MM, one looks for nucleoli in the plasma cells. Note also that the Golgi areas are not clearly demarcated in these cells. This, too, is an extremely abnormal finding.
Course Section: 10. Plasma Cell Dyscrasias
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