In acute lymphoblastic leukemia (ALL), the occult central nervous system (CNS) involvement appears to be associated with poor prognosis. Flow cytometry (FCM) allows detection of occult CNS localization. The current international guidelines do not recommend the use of FCM in the assessment of CNS at onset in adult ALL patients. Large-scale prospective studies will help to clarify whether or not patients with occult CNS localization should undergo CNS-directed therapy. Understanding this seems particularly important nowadays considering that with the introduction of new drugs (monoclonal antibodies, next-generation tyrosine kinase inhibitors, CAR-T) the therapeutic approach of patients with ALS is increasingly "chemo-free"

The investigators propose a multicenter prospective study to evaluate the incidence of occult CNS localization and the impact of such localization on clinical outcome.Adult ALL patients routinely undergo diagnostic lumbar puncture (PL); cerebrospinal fluids (CSF )samples will be studied by investigation of conventional cytology (CC) and FCM at the time of the first and subsequent diagnostic PLs.

Inclusion criteria.

• Patients aged more than18 years with diagnosis of ALL at onset undergoing diagnostic-therapeutic PL.
• Signed written informed consent in accordance with ICH/EU/GCP guidelines and national and local laws.

Exclusion criteria.

• Patients <18 years of age
• Diagnosis other than ALL
• Inability to perform PL

Adult patients affected by acute lymphoblastic leukemia