{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,31]],"date-time":"2026-10-31T01:20:49Z","timestamp":1793409649576,"version":"4.5.0"},"reference-count":47,"publisher":"BMJ","issue":"8","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["J Clin Pathol"],"accepted":{"date-parts":[[2026,5,25]]},"published-print":{"date-parts":[[2026,8]]},"abstract":"<jats:p>\n                    Transdifferentiation from follicular lymphoma (FL) to histiocytic\/dendritic cell sarcoma (HDS) is rare and requires molecular confirmation of shared clonal origin. Targetable mutations such as\n                    <jats:italic>BRAF<\/jats:italic>\n                    V600E may offer therapeutic opportunities in such aggressive neoplasms. We report an exceptional case of untreated localised FL transdifferentiated to an HDS after 18 years. Shared\n                    <jats:italic>BCL2<\/jats:italic>\n                    rearrangement and mutation profile confirmed a clonal link, while the HDS acquired an additional\n                    <jats:italic>BRAF<\/jats:italic>\n                    V600E mutation. Treatment with BRAF\/MEK inhibitors yielded a sustained 18-month clinical response. The disease later relapsed as high-grade B-cell lymphoma with\n                    <jats:italic>MYC<\/jats:italic>\n                    and\n                    <jats:italic>BCL2<\/jats:italic>\n                    rearrangements (HGBCL-\n                    <jats:italic>MYC\/BCL2<\/jats:italic>\n                    ), still harbouring the\n                    <jats:italic>BRAF<\/jats:italic>\n                    mutation. Complete remission was achieved with Rituximab, Cyclophosphamide, Hydroxydaunorubicin, Oncovin and Prednisone, but the double-hit lymphoma relapsed 14 months later.\n                  <\/jats:p>\n                  <jats:p>\n                    This case illustrates sequential transformation from FL to\n                    <jats:italic>BRAF<\/jats:italic>\n                    -mutated HDS with excellent response to BRAF\/MEK inhibition, followed by evolution into HGBCL-\n                    <jats:italic>MYC<\/jats:italic>\n                    \/\n                    <jats:italic>BCL2<\/jats:italic>\n                    responding transiently to immunochemotherapy, emphasising the value of repeated histological and molecular reassessment in FL evolution.\n                  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