The tumor-forming type of multiple myeloma. I. Biological behavior

A total of 45 cases of multiple myeloma has been followed up clinically during the period from 7 to 80 months. Out of these, six patients (13.3%) were diagnosed to be the tumor-forming type; they developed discrete tumor formation at the disease onset or during clinical observation. Biological behavior of these cases is briefly outlined. Histologically, five cases presented with well or moderately well differentiated plasma cells according to the grading made by Pasmantier and Azar. The remaining one case was poorly differentiated in cell maturity, and with electron and immunofluorescence microscopies, proved to be of plasmacytic nature.