Large lymphocytes with crystalline structures in their cytoplasm (Fig. 2A),
surrounded by ergatoplasmic membranes were observed in the bone marrow
and lymph nodes from a patient with monoclonal serum IgG K (kindly referred
by Dr. Oberling). The blood lymphocytes did not contain such crystals. Staining
of marrow fixed cells showed a strong positivity for y and K chains
restricted to the crystals (Fig. 2 B) and the presence of a few plasma cells
containing IgG K Most blood and bone marrow lymphocytes, including those
which contained the crystals, carried S. IgG K (Fig. 2C).