The size and number of bone marrow megakaryocytes in malignant lymphoma and their relationship to abnormalities in platelet count

Platelet counts were measured routinely in 718 volunteer blood donors and 124 patients with malignant lymphoma. When considered by gender, the mean platelet counts of the patients with malignant lymphoma were significantly increased when compared to controls (P < 0.01). In addition, 9% of males and 4% of females with lymphoma exhibited a thrombocytosis, in which their platelet counts exceeded the upper limit of the normal platelet count for control subjects (defined as 2 SDs in excess of the mean value). Megakaryocyte whole size, cytoplasmic and nuclear sizes, and megakaryocyte numbers were also quantified in bone marrow obtained from the iliac crest of 5 hematologically normal subjects and 26 patients with malignant lymphoma. Mean megakaryocyte sizes were significantly greater in subjects with lymphoma, when compared to control values (P < 0.05). No significant differences in megakaryocyte numbers in bone marrow were observed between the two groups. For subjects with malignant lymphoma, platelet count was found to be significantly positively correlated with megakaryocyte size. The results of this study suggest that the elevated platelet count associated with malignant lymphoma is mediated by an increase in the size of the megakaryocytes in the bone marrow.