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9 - Grade/differentiation unknown, not stated, or not applicable
Acute progressive histiocytosis X
Eosinophilic granuloma (if solitary lesion)
Hand-Schuller-Christian disease (if multiple lesions or visceral involvement))
Histiocytosis X [OBS]
Langerhans cell granulomatosis
Langerhans cell granulomatosis, unifocal
Langerhans cell histiocytosis, disseminated
Langerhans cell histiocytosis, generalized
Langerhans cell histiocytosis, mono-ostotic
Langerhans cell histiocytosis, multifocal
Langerhans cell histiocytosis, poly-ostotic
Langerhans cell histiocytosis, unifocal
Langerhans histiocytosis, NOS
Letterer-Siwe disease (if disseminated or visceral involvement)
Nonlipid reticuloendotheliosis [OBS]
This is a clonal neoplastic proliferation of Langerhans type cells that express CD1a, langerin and S100 protein, and shows Birbeck granules by ultrastructural examination.
(This neoplasm is reportable for cases diagnosed 2010 and later.) Some of the terms were also reportable for earlier years. Langerhans cell histiocytosis (LCH) can be localized to a single site, multiple sites within a single system (usually bone), or more disseminated and multisystem. The dominant sites of involvement in the SOLITARY FORM are bone and adjacent soft tissue (skull, femur, vertebra, pelvic bones, and ribs) and less commonly lymph nodes, skin, and lung. The MULTIFOCAL lesions are largely confined to bone and adjacent soft tissue. In MULTISYSTEM disease, the skin, bone, and bone marrow are the preferential sites of involvement. The liver and spleen are also common sites of involvement; however they are typically considered sites of metastases and not the primary site. The gonads and kidney appear to be spared even in disseminated forms.
Patients with unifocal disease are usually older children or adults who most commonly present with a lytic bone lesion, eroding the cortex. Solitary lesions at other sites present as mass lesions or enlarged lymph nodes. Patients with unisystem multifocal disease are usually young children who present with multiple or sequential destructive bone lesions often associated with adjacent soft tissue masses. Skull and mandibular involvement is common. Diabetes insipidus follows cranial involvement. Patients with multisystem involvement are infants who present with fever, cytopenia, skin and bone lesions, and hepatosplenomegaly. Pulmonary disease in childhood is clinically variable.
The clinical course is related to the stage of disease at presentation with 99% or greater survival for unifocal disease and 66% mortality for young children with multisystem involvement who do not respond promptly to therapy. Involvement of bone marrow, liver, and lung are regarded as high-risk factors. Progression from initial focal disease to multisystem involvement can occur, most usually in infants. Age, per se, is less important as an indicator than the extent of disease. Systemic and (rarely) multifocal disease can be complicated by hemophagocytic syndrome.
NOTE: Langerhans histiocytosis, unifocal (9752/1 om OCD-O-3 for 2001-2009) Langerhans cell histiocytosis, multifocal (9753/1), and Langerhans cell histiocytosis, disseminated (9754/3) are now grouped with the newly reportable Langerhans cell histiocytosis (9751/3).