Central nervous system involvement at diagnosis remains an obstacle to a long-term cure of patients affected by acute lymphoblastic leukemia. The investigators have previously reported that flow cytometry (FCM) is better than conventional cytology (CC) in demonstrating the presence of leukemic cells in the patients'(pts) cerebrospinal fluid (CSF), especially in samples with low cell counts. In the framework of the national Campus ALL program aimed at improving the management of adult ALL patients in the context of the GIMEMA protocols, in the present study the investigators retrospectively evaluated the incidence of occult CNS positivity and its impact on outcome in 241 adult pts with newly diagnosed ALL from 13 centers.

Demographic and of laboratory data of 241 adult patients with ALL were retrospectively recorded. All patients underwent diagnostic lumbar puncture and each cerebrospinal fluid sample was examined by CC and FCM. The investigators identified patients with the only FCM positivity and the investigators correlated this condition with clinical and of laboratory data and with clinical outcome.

Inclusion Criteria:

• ALL at onset
• Age >18 years

Exclusion Criteria:

• ALL relapsed or refractory
• Age <18 years

Adult patients affected by ALL underwent to diagnostic lumbar puncture