Polymerase chain reaction on cerebrospinal fluid cells in suspected leptomeningeal involvement in childhood acute lymphoblastic leukemia: comparison to cytomorphological analysis.

The leptomeningeal involvement of central nervous system is defined in the most centers by the presence of blast cells in the CSF or the presence of cranial-nerve palsies. Sometimes, cytology does not allow clear distinction between lymphoblasts and normal cells, and auxiliary methods to the precise identification of leukemic cells in cerebrospinal fluid is necessary. We analyzed CSF from 11 consecutive patients, in whom a differential diagnosis of leptomeningeal involvement was made, including 4 patients at diagnosis and 7 patients during the treatment by cytomorphological analysis and PCR and automatic sequencing. Six patients were considered with leptomeningeal involvement by conventional analysis: unequivocal cytomorphological involvement was considered in 5 patients, and in one it was assumed to be due to cranial-nerve palsy, with no blast cells detected in cerebrospinal fluid. In 2 it was considered suspicious and in 3 negative. PCR and sequencing analysis showed involvement in 6 patients; 5 of the 6 patients were considered to have leptomeningeal involvement based on clinical and cytomorphological criteria, and, in one of the patients, it was suspicious. Our data suggest that the use of PCR and sequencing can be useful in confirming CNS leukemia and eliminating other conditions when used together with the cytomorphological analysis.