The purpose of this study is to define if flow cytometry has more sensitivity for detecting neoplastic cells in cerebrospinal fluid versus conventional cytology.

Aggressive B-cell non-Hodgkin's lymphoma (B-NHL), Lymphoblastic Lymphoma and Burkitt's Lymphoma are at high risk of CNS relapse. For this reason is recommended a prophylaxis therapy. This suggests that negative leptomeningeal localization patients at diagnosis are really positive and that would be a very high risk of CNS relapse subtype patients. It's very important detecting neoplastic cells in cerebrospinal fluid as soon as possible. This study will evaluate only patients that have been flow cytometry and cytology at diagnosis.

Inclusion Criteria:

1. Diagnosis of

   • Diffuse large cell lymphoma HIV positive,
   • Lymphoblastic lymphoma,
   • Burkitt's lymphoma,
   • Mantle cell lymphoma blastoid type.

2. DLCL patients who presented one risk factor for leptomeningeal involvement as:

   • testis, bone marrow, orbit, palate, paranasal cavity or peridural disease localization,
   • 2-3 age-adjusted IPI score with more than 1 extranodal site and LDH > normal.

3. Patients with cytologic and flow cytometry on cerebrospinal fluid at diagnosis.

Exclusion Criteria:

1. Patients with clinical or strumental evidence of meningeal localization disease.

Patients affected by aggressive non-Hodgkin's lymphoma at diagnosis