Table 5.

Diagnostic criteria for Myeloproliferative neoplasms, unclassifiable (MPN-U) according to the International Consensus Classification¹

1. Clinical and hematological features of a myeloproliferative neoplasm are presenta

2. JAK2, CALR, or MPL mutationb or presence of another clonal markerc

3. Diagnostic criteria for any other myeloproliferative neoplasm, myelodysplastic syndrome, myelodysplastic/myeloproliferative neoplasmd, or BCR::ABL1-positive chronic myeloid leukemia are not met

The diagnosis of MPN-U requires all 3 criteria

^aIn cases presenting with BM fibrosis, reactive causes must be excluded, in particular BM fibrosis secondary to infection, autoimmune disorder or another chronic inflammatory condition, hairy cell leukemia or another lymphoid neoplasm, metastatic malignancy, or toxic (chronic) myelopathy

^bIt is recommended to use highly sensitive assays for JAK2V617F (sensitivity level < 1%) and CALR and MPL (sensitivity level 1–3%)—in negative cases, consider searching for non-canonical JAK2 and MPL mutations

^cAssessed by cytogenetics or sensitive NGS techniques; detection of mutations associated with myeloid neoplasms (e.g., ASXL1, EZH2, IDH1, IDH2, SF3B1, SRSF2, and TET2 mutations) supports the clonal nature of the disease

^dIn cases presenting with myelodysplastic features, effects of any previous treatment, severe comorbidity, and changes during the natural progression of the disease process must be carefully excluded