Study population
We collected bone marrow biopsies of patients with PMF done at Tulane
Medical Center from 1990 to 2019. All these patients had a known JAK2
status and a well-preserved specimen for adequate PD-L1 staining. We
only used the initial bone marrow biopsy obtained to diagnose patients
with PMF. We collected 10 additional samples of patients that came to
clinic with transient cytopenias from benign hematologic conditions.
These patients had normal karyotype, FISH panel for myelodysplastic
syndrome (MDS), and a negative 64-gene next generation sequencing (NGS)
myeloid mutation panel. An institutional review board approval was
obtained before collecting these bone marrow samples and all
participants gave informed consent. The authors analysed the data to
which all authors had access. All relevant participant data was
deidentified and shared as appropriate in the text.