Abstract
Langerhans cell histiocytosis (LCH; formerly histiocytosis X) is a neoplastic proliferation of Langerhans cells (antigen-presenting histiocytes). Involvement of osseous and extraosseous sites of the head and neck has been reported in as many as one-third of cases. Osseous LCH may involve the flat bones of the skull, the facial bones, the bones of the jaw and sinonasal tract, and the medial part of the external auditory meatus. Destructive bone lesions can manifest as headache, toothache, tooth loss, hearing loss, and otitis media. Involvement of the skull can also cause exophthalmos and diabetes insipidus.
Radiographically, bone lesions appear as sharp, punched-out radiolucencies. Sites of extraosseous involvement include the facial skin and scalp, the periorbital region, the gingiva, and the cervical lymph nodes.
Demographically, LCH occurs mainly in children (∼1/200,000 annually), it is rare in blacks, and it has a predilection for males (male-to-female ratio 3.7:1).
It is important to remember that while LCH may present as a solitary lesion (known as an eosinophilic granuloma), it can also be multifocal and involve several systems (e.g., the liver, spleen, lung, gastrointestinal tract, and central nervous system). In Hand-Schüller-Christian disease, there is multifocal involvement of a single tissue, usually bone. In Letterer-Siwe disease, there is multisystem involvement. Patients can also present with fever, rashes, and pancytopenia. The etiology of LCH is unknown.
Figure.
On tissue biopsy, the histopathology of LCH is distinctive. Lesions are characterized by an accumulation of mononuclear and multinucleated Langerhans cells admixed with abundant mature eosinophils (figure, A), as well as some neutrophils and small lymphocytes. Eosinophilic abscesses can feature central necrosis. Langerhans cells have grooved, folded, indented, or lobulated vesicular nuclei (figure, B). They are typically positive for immunohistochemical stains against CDla (figure, C), langerin, S-100 protein, and CD68. The hallmark of Langerhans cells is the ultrastructural presence of cytoplasmic Birbeck granules, which are rod- or tennis-racket-shaped structures (figure, D). LCH must be distinguished from reactive histiocytosis, Hodgkin lymphoma, NK/T-cell lymphoma, Erdheim-Chester disease (a CD la-negative histiocytic disorder), and Rosai-Dorfman disease.
Patients with treated unifocal LCH have an excellent prognosis, but the presence of multisystem involvement is a poor prognostic sign. Unifocal disease progresses to multisystem disease in about 10% of patients. Spontaneous regression has occurred in rare cases. The choice of treatment depends on the number of sites involved. Solitary lesions, which frequently occur in the head and neck, can be conservatively resected with curettage or excision. Systemic chemotherapy is administered to patients with disseminated or multifocal disease and to those who do not respond to local treatment.