Mesenchymal stem cells from JAK2(V617F) mutant patients with primary myelofibrosis do not harbor JAK2 mutant allele.

These data provide a possibly definitive support to the concept of the “paraneoplastic” nature of stromal reaction in PMF by showing that homogeneous preparation of MSCs obtained in vitro from mutant patients with primary or post-polycythemic myelofibrosis, or with PV, are JAK2V617F negative. The possibility that a rare population of MSCs har-boring the JAK2 mutation has been lost in culture because of selective overgrowth of normal MSCs could not be ruled out in this experimental system, but it seems highly unlike