{
  "abstract": "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 BRAF 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 BCL2 rearrangement and mutation profile confirmed a clonal link, while the HDS acquired an additional BRAF 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 MYC and BCL2 rearrangements (HGBCL-MYC/BCL2), still harbouring the BRAF mutation. Complete remission was achieved with Rituximab, Cyclophosphamide, Hydroxydaunorubicin, Oncovin and Prednisone, but the double-hit lymphoma relapsed 14 months later.This case illustrates sequential transformation from FL to BRAF-mutated HDS with excellent response to BRAF/MEK inhibition, followed by evolution into HGBCL-MYC/BCL2 responding transiently to immunochemotherapy, emphasising the value of repeated histological and molecular reassessment in FL evolution.",
  "authors": [
    {
      "affiliations": [
        ", Institute of Pathology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Claire Royer-Chardon"
    },
    {
      "affiliations": [
        ", Institute of Pathology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Bettina Bisig"
    },
    {
      "affiliations": [
        ", Institute of Pathology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Mounir Trimech"
    },
    {
      "affiliations": [
        ", Institute of Pathology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Baptiste Guey"
    },
    {
      "affiliations": [
        ", Institute of Pathology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Edoardo Missiaglia"
    },
    {
      "affiliations": [
        "Service of Hematology, Department of Oncology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Sophie Voruz"
    },
    {
      "affiliations": [
        "Service of Interventional Radiology, Department of Diagnostic and Interventional Radiology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Alban Denys"
    },
    {
      "affiliations": [
        "Service of Hematology, Department of Oncology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Anne Cairoli"
    },
    {
      "affiliations": [
        ", Institute of Pathology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital (CHUV) and Lausanne University, Lausanne, Switzerland"
      ],
      "name": "Laurence de Leval"
    }
  ],
  "title": "Secondary BRAF-mutated histiocytic/dendritic cell sarcoma transdifferentiated from follicular lymphoma with prolonged response to BRAF/MEK inhibition and subsequent evolution to high-grade B-cell lymphoma",
  "uid": "ffc2341b-0f9c-5a07-9338-425ea9300cdf"
}