Assessment of Disease Burden in Hairy Cell Leukemia

Inclusion Criteria:

1. Histologically confirmed diagnosis of HCL patients:

   1. newly diagnosed and candidates for first-line cytoreductive treatment with analogues purines or
   2. in relapse after a previous line of treatment, with indication for rescue therapy (repetition of a purine analogue; use of targeted or innovative drugs), except splenectomy or
   3. in CR for at least 5 years after a first line of treatment, in the absence of clinical alterations indicative of a state of hematological relapse, or in any case in the absence of an indication for a new line of cytoreductive therapy (time-to-next treatment exceeding 5 years).
2. Age ≥ 18 years at enrollment
3. Signature of written informed consent

Exclusion Criteria:

1\. Concomitant second malignancy.