SP27 | CAN MAST CELL INFILTRATION INFLUENCE MYELOPROLIFERATIVE DISORDERS?

Background Mast cells have been associated with fibrosis in different tissues, organs, and disease processes including hematopoietic malignancies. In patients with primary bone marrow disorders, cold be an increase of mast cells in their bone marrow. Endpoints The primary objective of this study is to analyze clinical differences between patients with bone marrow mast cell infiltration and patients without it. Methods We collected bone marrow biopsies of patients with chronic myeloproliferative syndromes diagnosed from 2020 to 2024. 145 bone marrow biopsies have been collected during this period, and were categorized as follows: 35 samples were from patients with idiopathic myelofibrosis, 62 samples were from patients with essential thrombocythemia, 32 samples were from patients with polycythemia vera, and 9 samples were from patients with chronic myeloproliferative syndrome not otherwise specified. We have considered the following clinical characteristics: splenomegaly, blood counts, degree of fibrosis. Results The population was homogeneous in terms of sex and driver mutation type. At disease onset, about 51 % of the population (75 pts) had no sign of mast cell infiltration, whereas 49% of the population (70 pts) had significant mast cell infiltration. There were no differences in blood counts [P=0.67] or splenomegaly (P=0.19) respectively. There was a statistically significant difference, as a fibrosis grade of 2-3 was identified in 16 pts(11,0%) in the group with mast cell infiltration, whereas only 4 pts (2,8%) in the group without such infiltration exhibited the same grade (P=0.002). During this time frame, 14 patients had disease progression from essential thrombocythemia or polycythemia vera to myelofibrosis o myeloide leukemia. At the onset of the disease, none of the fourteen patients presented mast cell infiltration. Mast cell infiltration was shown in 10 patients at the progression of the disease. In a sub-analysis conducted in a sample of 35 patient with idiopathic myelofibrosis, the majority of subjects showed mast cell infiltration (22 pts), 16 patients of whom(73%) presented grade 2-3 fibrosis. In the remaining population (13 pts) only 30%(4 pts) presented grade 2-3 fibrosis. Conclusions In this retrospective analysis, it was observed that, within the group of patients exhibiting mast cell infiltration, there was a higher number of patients with grade 2-3 fibrosis. Mast cell infiltration can contribute to increase bone marrow fibrosis.