Chronic "Philadelphia-negative" myeloproliferative syndromes are chronic blood disorders. They include essential thrombocythemia, polycythemia vera, and myelofibrosis. Myelofibrosis may arise de novo ("primary myelofibrosis") or represent the evolution of essential thrombocythemia or polycythemia vera ("secondary myelofibrosis").

The myelofibrotic stage-characterized, as the name implies, by the presence of bone marrow fibrosis (deposition of scar-like tissue)-is generally associated with a more severe and symptomatic disease. To date, the only way to assess fibrotic progression in these disorders is bone marrow biopsy.

The aim of this project is to evaluate whether the identification, tracking, and quantification of cells expressing a specific receptor (CCR2), a selective biomarker of fibrosis, may allow early and non-invasive identification of the fibrotic stage of the disease through:

• laboratory analysis on a blood sample (using flow cytometry)
• use in PET-CT (positron emission tomography combined with computed tomography) of a tracer specific for the CCR2 receptor, capable of selectively binding to CCR2-expressing cells (⁶⁸Ga-DOTA-ECL1i).

It is well established that the presence of bone marrow fibrosis in Philadelphia-negative myeloproliferative neoplasms (MPNs) defines a more severe disease stage, with a worse prognosis and a high risk of leukemic transformation. Therefore, accurate allocation of each patient to the correct diagnostic category is essential for subsequent therapeutic planning, which may also include bone marrow transplantation for selected patients.

To date, the only method available to assess bone marrow fibrosis is histopathological analysis of the bone marrow, which inevitably requires an invasive procedure such as bone marrow biopsy.

The aim of this project is to evaluate whether tracking and quantification of CD34⁺CCR2⁺ cells through flow cytometry (FCM) on peripheral blood and functional imaging may represent a valid non-invasive tool for identifying the fibrotic stage of the disease, thus supporting clinicians at key diagnostic time points, such as:

At disease onset, in support of histopathology for differential diagnosis when morphological features alone may be ambiguous (e.g., ET vs prePMF, unclassifiable MPNs); During follow-up, in cases of suspected progression of ET/PV to secondary myelofibrosis (SMF), as a screening tool prior to bone marrow biopsy; As an alternative to bone marrow biopsy, when clinical conditions do not allow the procedure.

To this end, the project is structured around the following AIMS:

AIM 1 - Tracking of CD34⁺CCR2⁺ cells by flow cytometry as a diagnostic tool supporting histopathology in the differential diagnosis of MPN subtypes.

AIM 2 - Functional imaging of CCR2⁺ cells using the radioligand ⁶⁸Ga-DOTA-ECL1i in a murine model of myelofibrosis.

AIM 3 - Functional imaging of CCR2⁺ cells using the radioligand ⁶⁸Ga-DOTA-ECL1i in patients affected by MPNs.

Inclusion Criteria:

• Diagnosis of ET/PV/prePMF/overtPMF according to the WHO 2016 criteria and of SMF according to the IWG-MRT criteria (with histopathological data).
• Age >= 18 yrs
• ECOG performance status <=3

Exclusion Criteria:

• Pregnancy/breastfeeding
• Ongoing therapy with immunomodulatory drugs (JAK-inhibitors, interferon).
• For PET imaging, patients should be off any cytoreductive treatment for at least 3 months.
• Antiplatelet agents are allowed