Acute lymphoblastic leukemia, hand-mirror variant. A detailed ultrastructural study.

The hand-mirror cell in acute lymphoblastic leukemia may have important immunologic, pathogenic, and prognostic implications. To learn more about this cell, a detailed ultrastructural analysis was performed. Fifty electronmicrographs of lymphoblasts from an untreated patient with acute lymphoblastic leukemia with numerous hand-mirror cells in the bone marrow were compared with 60 electronmicrographs of lymphoblasts from six patients with classic acute lymphoblastic leukemia. The unique qualitative ultrastructural features of the hand-mirror cells were the presence of undamaged mitochondria and uropods (handles) with terminal microspikes containing circular organized arrangement of 50-A microfilaments. Quantitative differences between hand-mirror cells and lymphoblasts were observed in nuclear perimeters (P less than 0.0001), nuclear lengths (P less than 0.001), cytoplasmic lengths (P less than 0.0002), nuclear-cytoplasmic length ratios (P less than 0.0001), and numbers of mitochondria (P less than 0.002). These findings indicate that hand-mirror cells contain ultrastructural components that are related to cell motility and the immunologic process. These results are significant in that the hand-mirror cells may be associated with an immunologic mechanism that is involved in leukemogenesis.