Nucleolar Size in Benign and Malignant Plasma Cell Proliferation

Abstract Nucleolar and nuclear size of bone marrow plasma cells has been studied in 26 cases of myeloma, 19 of benign essential monoclonal gammapathy (BEMG) and 9 without an M‐component. Bone marrow smears were Feulgen‐stained to visualize nucleoli and nuclei. Nucleolar area, nuclear area and the ratio nucleolar area/nuclear area were calculated. The myeloma group differed from the other two groups in having plasma cells with larger nucleoli, larger nuclei and an increased ratio nucleolar area/nuclear area. No difference was found between the BEMG group and the cases without an M‐component. In some cases—in which the absence of osteolytic lesions at X‐ray examination, a low plasma cell percentage in bone marrow smears or a low M‐component concentration initially made the diagnosis of myeloma uncertain—the observation of enlarged nucleoli could help to establish the diagnosis. Three cases were observed in which the onset of myeloma was preceded by a long period of essentially unchanged M‐component concentration. In these cases a sudden increase of M‐component concentration was accompanied by an increase of mean nucleolar size of bone marrow plasma cells.