Pediatric myelofibrosis: WHO 2024 update on myeloproliferative neoplasms calling?

OBJECTIVES: Pediatric myelofibrosis is a rare entity with the largest reported series of 19 cases. We describe here the clinicopathological spectrum and outcomes of 15 cases of pediatric myelofibrosis. METHODS: Case files of myelofibrosis of patients less than 18 years were retrieved from January 2016 to January 2019, and patients with idiopathic myelofibrosis after exhaustive work-up were studied. Their clinicopathological profiles were studied and then followed up for resolution and malignant transformation. RESULTS: Of the 15 cases of idiopathic myelofibrosis, transfusion-dependent anemia (14/15) was most common presentation. Only one patient showed leukoerythroblastosis with dacryocytes. Myeloid hyperplasia was seen in 13 of 15 patients and megakaryocytic hyperplasia in 10 patients. Dysmegakaryopoiesis was seen in 8 of 15 patients, and only three had small loose megakaryocytic clustering. None showed hyperchromatic megakaryocytes, intrasinusoidal hematopoiesis, or osteosclerosis. One patient with trisomy 8 tested positive for JAK2V617F. Bone marrow biopsy was hypercellular in 13, and 8 had world health organization (WHO) MF-3 fibrosis. None of the patients developed malignancy, one had spontaneous resolution, and one patient required allogenic stem cell transplant. CONCLUSIONS: Pediatric myelofibrosis is a distinct entity from primary myelofibrosis in adults and merits mention in the WHO manual as a distinct entity.