Our case n°2 was re-biopsied at the time of CML partial MR and the histology switched from CML+fibrosis to a phenotype suggestive of JAK2+MPN with fibrosis, in particular the MKs from small-sized, non-clustering forms changed to variably sized, clustering MKs. The gene discussed is JAK2; the disease is myeloproliferative neoplasm.