Multiple myeloma associated with multilobated plasma cell nuclei.

Ten cases of multiple myeloma are reported in which there were a large number of plasma cells with excessively convoluted or lobulated nuclei. These cases represent 3% of the 297 evaluable multiple myeloma patients treated at our institution over a 22-year period. All 10 had intermediate or advanced stage disease at the time of diagnosis, and all have died after a mean survival of 19.5 months. Ultrastructural features of 2 cases are described. When found in abundance, such cells can cause difficulty in establishing a morphologic diagnosis of multiple myeloma because of their resemblance to other cell types. Therefore, it may be necessary to perform immunoperoxidase staining and/or electron microscopy to confirm the plasmacytic identity of these cells. The findings add further support to the contention that the presence of excessive nuclear convolutions is not a completely reliable indication of T-cell, as opposed to B-cell, lineage.