Langerhans Cell Histiocytosis, Non-Langerhans histiocytosis and concurrent Papillary Thyroid Carcinoma with BRAF V600E mutations: A case report and literature review

摘要

Langerhans Cell Histiocytosis (LCH) and the non-LCH, Erdheim Chester Disease, are rare histiocytic neoplasms with distinctive clinical and immunophenotypic features, but with several overlapping mole- cular features. LCH is a neoplasm of Langerin-positive, CD1a-positive, $100-positive dendritic cells (DCs), once thought to arise from the epidermal or mucosal-derived Langerhans Cell (LC) due to the mor- phologic, immunophenotypic, and ultrastructural similarities between neoplastic LCH cell and the physiologic LC [5,6]. However, gene ex- pression profiling studies of LCH cells have shown that these cells are not derived from terminally differentiated LCs as originally thought, but rather share a closer kinship with dendritic cells of the bone marrow than with LCs of the skin [5-7]. LCH presents most often as a solitary lesion involving the bone, lymph node, skin or lung, but may also present with multifocal lesions or multisystemic disease, additionally involving the liver, spleen and bone marrow. Although LCH displays a broad spectrum of clinical presentations, histologically, all lesions in- clude prototypic LCH cells in an inflammatory background, often with admixed eosinophils and T-cells, leading those who originally studied the disease to question the neoplastic versus the reactive or in- flammatory nature of the lesion [8].