This case demonstrated a concurrent involvement of a lymph node by CHL and LCH, which was exceedingly rare. It has been controversial if LCH associated with lymphoma represents a true neoplasm, highlighted by a recent finding that there were no BRAF or MAP2K1 mutations in LCH. Our case may represent the first demonstration of BRAF V600E mutation in a typical case of LCH associated with lymphoma, supporting that at least some of the LCHs associated with lymphoma are true neoplasm. The twice-confirmed low allele frequency for the BRAF V600E mutation despite microdissection could point to an early clonal event in the background of an initially reactive Langerhans cell proliferation.
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