Vacuolated plasma cells in multiple myeloma.

Practically all myeloma cells had prominent vacuoles, around and within which the end product of acid phosphatase (AP) reaction was demonstrated. These vacuoles were considered to be autophagic. In remission, only a few myeloma cells were vacuolated. Serial determinations showed transition from an initial high AP score (3.86) to a low score (1.32) in remission. Moreover, there was a trend towards a lower average percentage of positive cells in remission (72%) as compared to the preinduction phase (100%). Intracellular Bence Jones proteins of the present case may be toxic and capable of causing vacuolation with activation of lysosomal enzymes.