The study is designed as a retrospective analysis of patients with relapsed/refractory FL identified by the hematological centers of Italy.

The study does not require any intervention on the patient, but it involves the simple collection of data that are already present in the medical record. Since this is a retrospective study, it will not require further analysis or diagnostic investigations than those already made.

Inclusion Criteria:

• Patients with initial diagnosis of follicular lymphoma since 2001
• Histological confirmation of follicular lymphoma, grade I, II, III according to WHO 2008 classification, at the time of initial diagnosis
• Systemic first-line treatment with immuno-chemotherapy
• PET availability at the time of response after first-line treatment (optional)
• Clinical and radiological evidence of FL relapse or progression
• Histological confirmation of relapse (strongly recommended)
• PET availability of at the time of relapse/progression and images available for central assessment
• Availability of clinical, laboratory and therapeutic treatment data at the time of initial diagnosis and relapse/progression
• Follow up of at least 12 months after relapse/progression

Exclusion Criteria:

• None

Patients with relapsed/refractory FL identified by the hematological centers of Italy