Virus-bearing plasma cells in peripheral blood of a patient with 'hairy cell' leukemia.

Electron-microscopic examination of peripheral blood from a patient with 'hairy cell' leukemia revealed classical 'hairy cells', atypical lymphoid cells and numerous pathological plasma cells. Osmiophilic granular material coated the cell surface of 'hairy cells' and lymphoid cells but not the plasmalemma of the plasma cells. The most important features of the plasma cells were cytoplasmic protrusions and masses of oncogenic virus A particles in their endoplasmic reticular cisternae.