Differentiation of plasma and myeloma cells of man. Combined planimetric and cytophotometric studies.

Plasmacytoid cells in the bone marrow of 3 patients with myeloma and plasma cells in the bone marrow of a 6-year-old boy with an infectious disease were assessed cytophotometrically, first after Giemsaand second after Feulgen staining. The cell and nuclear surface and the nuclear/cytoplasmic ratio were determined from the number of measuring points. The nuclear DNA content of individual cells was registered and the distribution of DNA within the nucleus was assessed by the distributional error. Both the mean nuclear/cytoplasmic ratio and the distributional error of myeloma cells varied from patient to patient but could not be used to differentiate between normal plasma cells and myeloma cells. It was not possible either to differentiate these cell types by multiplying the mean nuclear/cytoplasmic ratio with the mean distributional error of the nuclear DNA. A strong correlation between cell and cytoplasmic surface area was observed both in normal plasma cells and in myeloma cells.