Overt and Masked Polycythemia Vera Within the Scope of Ph-Negative Myeloproliferative Diseases

Abstract

Aim. To study the structure of Ph-negative myeloproliferative diseases (Ph- MPD) and to identify morphological markers for diagnosing masked polycythemia vera (PV). Materials & Methods. Bone marrow core biopsy samples from the database of pathology department of National Research Center for Hematology within the period from January 2014 to June 2017 provided the basis for analyzing the diagnosed Ph- MPD cases. The trial included the bone marrow core biopsy samples of the patients treated and fol-lowed-up not only at the National Research Center for Hematology but also at other medical centers in the Russian Federation in the context of clinical, laboratory and molecular data. Results. In 1611 Ph- MPD patients PV prevailed corresponding to 40.6 % of all cases. In the PV group the masked form was diagnosed in 29 % of patients. Primary myelofibrosis (PMF) was diagnosed in 26.6 % of all patients including 10 % of cases with pre-fibrosis/early stage. The 3d most frequent disorder was essential thrombocythemia (ET) which corresponded to 16 %. JAK2 driver mutation was identified in all 654 PV patients. In 4 cases out of them exon 12 mutation was detected. A similar mutation was found out in PMF (53 %) and ET (60 %). In 36 % of PMF patients and 27 % of ET patients CALR mutation was detected. MPL mutation was identified in 4 % of PMF cases and was not discovered in ET. Triple negative patients were identified in 7 % of PMF and 13 % of ET cases. The designation of “myeloproliferative disease unclassifiable” can be applied to 16.8 % of cases. The trial deals with morphological criteria for diagnosing masked PV during examination of bone marrow core biopsy samples. In 30 % of patients with masked PV (according to the 2017 WHO classification) and splenomegaly (> 14 cm) portal vein thrombosis was identified. Conclusion. In the Ph- MPD group PV diagnosis prevailed (40.6 %). The histological analysis of bone marrow core biopsy samples of the patients with the masked PV accounting for 29 % of all PV cases, revealed morphological features typical of overt PV. Histological analysis of bone marrow is a reliable method for diagnosing overt and masked PV. Among morphological characteristics of the bone marrow of patients with masked PV and portal vein thrombosis special attention should be paid to the MF-1 grade of reticulin fibrosis (29 % of cases) and loose clusters of megakaryocytes (71.4 %).