Recent advances in hematology clearly illustrate that the simple "clonal" nature of various hematological malignancies may not really reflect the reality of malignant cells natural expansion. This has been nicely illustrated in recent works in AML for example where subclones coexists in the same patient at the same time, but could also differentially expand over time because of effects of therapeutics intervention, but also by oncogenic spontaneous events (1).

These observations have been done recently because of next generation sequencing that allows to discriminate in the same tumor samples, different subclones and to analyse the clonal architecture. Sequential analyses could help us to identify the first oncogenic event and to correlate disease progression to the emergence of subclones.

For all these reasons it is of a major interest to precisely understand the architecture of the clone in MPNs, especially to understand which is the initiating event and how from this initial event the clone develops.

In MPNs in which JAK2V617F is the initiating event, its targeting is expected to be extremely effective. If JAK2V617F is a secondary event its targeting might allow to alleviate the MPN, but may favor the development of other malignant hemopathies.

Inclusion Criteria:

• Patients with a malignant hematological disease.
• Signed written informed consent
• Age and Sex : men and women aged 18 years or older
• Patients affiliated to a social security system

Exclusion Criteria:

- Patients protected by law, in accordance with Articles L1121-L1121-5 to 8 of the Code of Public Health.