MPL immunohistochemical expression as a novel marker for essential thrombocythemia and primary myelofibrosis differential diagnosis.

To evaluate the grading of fibrosis and immunohistochemical expression of MPL in bone marrow biopsies of ET and PMF. Fibrosis in bone marrow biopsies (BMBs) was evaluated according to the European Consensus for grading of fibrosis, according to reticulin proliferation. Immunohistochemical analysis was performed in samples from 18 ET and 38 PMF patients: 19 were classified as pre-fibrotic and 19 were classified as fibrotic according to the World Health Organization (WHO) criteria, by means of the MPL antibody. Six bone marrow donors' biopsies were used as controls. Average reticulin (p<0.003) and MPL (p<0.008) values differed significantly between the ET group and the pre-fibrotic stage PMF group. The MPL immunohistochemical expression may represent a new marker for differential diagnosis between ET and pre-fibrotic stage PMF.