Proliferative kinetics of the leukemic cells in meningeal leukemia

Abstract

The proliferative kinetics of leukemic cells was investigated in the cerebrospinal fluid (CSF) and the leptomeninges of 5 patients with meningeal leukemia (ML) and 15 selected autopsies showing meningeal involvement. The 3H-thymidine labeling index (TLI), mitotic index (MI) and 3H-uridine labeling index (ULI) of leukemic cells in the CSF at the time of diagnosis were 0.7 ± 0.2, less than 0.01 and 96.2 ± 0.7%, respectively. The TLI was found to be higher at the time of recurrence than at the initial diagnosis of meningeal leukemia. The grade of leukemic cell infiltration was classified according to Price's criteria. The mitotic index was also estimated on the histologic sections. An infiltration of Grade 2 or greater was observed in all 4 patients who had not received an intrathecal administration of methotrexate (MTX). The clinical course of 2 patients with a higher MI (0.88 and 0.32%) was shorter than the other 2 (0.03 and 0.01%). In the patients who did not show clinical manifestations of ML, the infiltration of leukemic cells in the leptomeninges was mild in degree, and the MI was less than 0.01%. Likewise, mild infiltration and low MI was observed in 8 cases treated with an intrathecal administration of methotrexate. These findings seem to support the general concept that the proliferation of leukemia cells infiltrating leptomeninges is remarkably slow at an incipient stage of ML; then it undergoes a gradual acceleration, possibly slowing down again at an advanced stage of the disease.