Histiocytic diseases arise from MAPK mutations in myeloid progenitors. Depending on whether the progenitor follows a dendritic cell or macrophage/monocyte lineage the final histology results in Langerhans cell histiocytosis, Rosai-Dorfman disease or Erdheim-Chester disease. Commentary on: Friedman et al. Mixed histiocytic neoplasms: A multicentre series revealing diverse somatic mutations and responses to targeted therapy. Br J Haematol 2024;205:127-137.
Keywords: MAPK mutations; histiocytic diseases; myeloid progenitors.
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