Myeloma plasmacytes were studied in six untreated patients to obtain more information on the nuclear ultrastructural abnormalities in these cells. Asynchrony of nucleolar, nuclear, and cytoplasmic maturation was frequently observed in pleomorphic myeloma plasmacytes. Immature and mature myeloma plasmacytes of two patients contained intranuclear rodlets which consisted of fine filaments arranged in parallel. Myeloma plasmacytes in mitosis often contained persistent nucleoli, nucleolar fragments, and small nucleolus-like bodies. The mitotic division of the nucleus was also noted in differentiated cytoplasm. In some cells in mitosis, the cytoplasm was differentiated and apparently functional.
This work was supported by Cancer Research Center Grant CA-10893-P.5.