Histiocytoses non-langerhans cell histiocytosesD76.3

The non-Langerhans cell histiocytoses are grouped under the name"xanthogranulomas" to show the affiliation of clinically different diseases that show histological similarities to xanthogranulomas.

They are mono- (skin, bone, lymph nodes), more rarely polyorganic, localized or generalized, benign neoplasms due to proliferation of cells of the monocyte-macrophage series. The diagnosis of "non-Langerhans cell histiocytosis" is made by the absence of electron-optical and immunohistological characteristics of Langerhans cells.

With the monoclonal antibody MS-1 (high molecular weight protein) a marker seems to have been found which is strongly expressed in lesional macrophages of non-Langerhans cell histiocytoses. This may suggest that disease patterns such as:

• the generalized eruptive histiocytomas
• benign cephalic histiocytosis
• multicentric reticulohistiocytosis
• xanthoma disseminatum or
• the juvenile xanthogranuloma

are different morphological expressions of a single disease entity.

Also, the ability or "inability" to store fat, previously listed as a differentiating feature of individual diseases, is more likely to be attributed to different stages of development (example: xanthomatous or non-xanthomatous variant of juvenile xanthogranuloma). The nosological status of histiocytoma (cell-rich dermatofibroma) is as controversial as that of normolipemic xanthomatoses or xanthelasma.

Even in dermatofibromas (old nomenclature: histiocytomas), the storage capacity (e.g., hemosiderin) cannot be taken as an expression of a separate type of tumor. It is rather to be seen as a functional restitution of a cell per se capable of phagocytosis.

Within the group of non-Langerhans cell histiocytoses(xanthogranuloma family, see Clinical and further classification there), 2 subgroups can be distinguished from a clinical point of view:

• Systemic non-Langerhans cell histiocytosis: Systemic Langerhans cell histiocytosis is dermatologically irrelevant and is dealt with in pediatric textbooks.
• Cutaneous non-Langerhans cell histiocytosis:
  • Classical cutaneous non-Langerhans cell histiocytosis (MS-1-)
  • Spindle cell cutaneous non-Langerhans cell histiocytosis (MS-1±).

See Table 1.

Classification of cutaneous non-Langerhans cell histiocytosis (varies according to Goerdt)

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