Langerhan’s cell histiocytosis (LCH) is a rare and clinically diverse disease that often confuses clinicians in terms of diagnosis and treatment. Due to the rarity of the disease, no definitive epidemiological studies are available. The etiology and pathology of Langerhans histiocytosis LCH is not known to date, whether it is an abnormal Langerhans cell hyperplasia or a pathological accumulation of normal Langerhans cells is not clear, and immune dysregulation is an important factor contributing to the development of this disease. Although most LCH is not a malignant disease, the responsibility of diagnosing and treating this disease often falls on the clinical oncologist. Modern pathological studies have shown that the histopathology of LCH, a group of diseases characterized by reticuloendothelial cell proliferation, has similar features, i.e., the proliferation, infiltration and accumulation of large numbers of Langerhans cells and their precursor cells at the site of invaded tissue. Microscopically, Langerhans cells are seen, characterized by an invaginated nucleus and a low nucleoplasmic ratio; LCH lesions are largely observed to be granuloma-like, with a predominantly histiocytic or histiocytic and eosinophilic infiltration, with eosinophilic infiltration being more common in osteolytic lesions. It is now clear that Langerhans cells in LCH are capable of producing multiple cytokines and responding to multiple cytokines; intercellular interactions and immune dysregulation may be the pathological basis for LCH. Molecular biology studies showed that Langerhans cells in LCH highly express lymphocyte functional antigen-3 and leukocyte adhesion molecule-1, while Langerhans cells in normal epithelium do not express them, suggesting that pathological Langerhans cells are not consistent with normal Langerhans cells. Clinical manifestations and diagnosis of Langerhans’ histiocytosis LCH occurs in children and adolescents, but adult cases are also reported, with an age of onset of 1 to 40 years, averaging about 9 years. Other clinical manifestations include chronic otitis media, uveitis, fever, weight loss, pain, masses, and enlargement of the liver, spleen, and lymph nodes. Osteolytic destruction is the most typical clinical manifestation of LCH, and the most commonly invaded bones are the skull, long bones, and ribs; if the lesions invade the ear or oral and maxillofacial areas, local symptoms are the main manifestation, and the jaws are invaded with loose teeth and swollen gums; patients with lesions invading the ear have headaches, dizziness, balance dysfunction, and uremia. In some cases, lymph node enlargement may occur. Widely disseminated cases tend to invade a variety of tissues and organs, including bones, skin, lymph nodes, thymus, liver, spleen, lungs, bone marrow, and central nervous system. There are three subtypes of LCH: LCH with single or multiple bone destruction called osteosarcoma, locally disseminated bone destruction with extraosseous soft tissue invasion (pituitary invasion and proptosis) (called Hand-Schiiller-Christian syndrome), and multiorgan and multisystem (e.g., liver, spleen, lung, bone marrow) involvement. The widely disseminated form (called Letter-Siwe syndrome) is associated with significant systemic symptoms. LCH has a low incidence, is rare, has a wide range of symptoms, is easily misdiagnosed, and has a low first-time diagnosis rate. systemic disease. The multi-system disease category is divided into a low-risk group (multi-organ system invasion without affecting the hematopoietic system, liver, spleen, or lung) and a high-risk group (multi-organ system invasion including the hematopoietic system, liver, spleen, and lung). The incidence is about two times the sum of the latter two. The treatment of Langerhans histiocytosis is based on the proper recognition and diagnosis of the various subtypes of LCH, which contain several subtypes, and it is difficult to diagnose the specific subtypes based on clinical experience alone, but accurate differentiation of the subtypes is essential, and the treatment of the different subtypes is different. For LCH lesions that eventually regress spontaneously, the choice of treatment should be based on the ability to stop the development of the lesion without causing irreversible damage to normal tissues, without requiring complete eradication of the lesion, especially in the treatment of pediatric cases. Current treatment of mild LCH is more conservative, and when treatment is required, it is often with vincristine or VP-16 monotherapy with or without hormones, or with low-dose local radiotherapy. Patients with limited lesions confined to a certain area are treated with radiotherapy or surgery and low-dose hormone therapy when necessary; patients with multiple lesions and extensive involvement need systemic drug therapy plus local radiotherapy can delay the progression of the disease. Specific treatment choices should be based on clinical staging and grading, and treatment reference programs are: (1) limited single systemic lesions (skin, bone or lymph nodes), with options of follow-up observation, local steroid hormone therapy, local surgical excision, and local low-dose radiotherapy (5-10 GY); (2) multiple single systemic lesions, with options of local surgical excision, local low-dose radiotherapy (5-10 GY), vincristine ( VBL) or VP-16 monotherapy plus prednisone regimen for 24 weeks; (3) multi-systemic lesions, either vincristine (VBL) + prednisone regimen with or without methotrexate (MTX), total treatment duration of 1 year; (4) other treatments, including nucleoglycan inhibitors (2-chlorodeoxyadenosine), CD1a monoclonal antibodies, hematopoietic stem cell transplantation therapy, and retinoic acid/pinealin therapy for central invasion ; (5) Support symptomatic treatment with Chinese herbal medicine. Prognosis of Langerhans histiocytosis The prognosis of LCH is varied, most cases can undergo a self-healing process, and LCH cases without vital organ involvement have a good prognosis and no life-threatening effects. Age at presentation and visceral organ involvement are important prognostic factors. The prognosis of widely disseminated LCH and LCH with multi-organ invasion is poor, and the prognosis of patients with visceral organ invasion at the time of presentation, such as liver, lung, and bone marrow invasion with organ dysfunction, is poor, especially for liver involvement.