Malignant blast cells in the cerebrospinal fluid.

In the cerebrospinal fluid of 45 patients, 240 cytological examinations has been performed. Sixteen patients were investigated serially in the course of intrathecal methotrexate treatment. The different mechanisms of nuclear fragmentation, various types of cytoplasmic vacuoles and the features of the reticulo-histiocytic reactions due to methotrexate has been analyzed. The morphological changes caused by methotrexate are attributed to depend on the cell type and on its response to therapy.