JAK2 and myeloproliferative neoplasm: In this case, bone marrow biopsy revealed normocellular marrow with moderate reticulin fibrosis but no overt MPN features; normal megakaryocyte morphology excluded pre-fibrotic MF, supporting a latent MPN diagnosis, with the 17% JAK2 V617F variant allele frequency likely explaining the absence of hematologic abnormalities [9].