Nonlangerhans Cell Histiocytosis at a Glance
- A broad group of disorders characterized by the proliferation of histiocytes involving cells other than Langerhans cells.
- Not rare. Most cases are in infants and run a benign, self-healing course lasting a few years.
- The primary histopathologic feature is a dense, diffuse infiltrate that is less epidermotropic than in Langerhans cell histiocytosis (LCH) and composed of occasionally foamy macrophages intermingled with lymphocytes, plasma cells, eosinophils, and sometimes Touton giant cells.
- In typical cases, histiocytes are CD68+ but CD1a– and CD207–.
- Most common sites of involvement are the head, trunk, and skin folds, with mucosal lesions rare.
- Systemic manifestations such as ocular involvement, diabetes insipidus, and joint and visceral impairment are rare in juvenile xanthogranuloma, the most common type of non-Langerhans cell histiocytosis (NLCH), but are common in the rarer forms of NLCH.
Non-Langerhans cell histiocytosis (NLCH), or class II histiocytosis, represents a broad group of different disorders characterized by the proliferation of histiocytes other than Langerhans cell (LC) (Table 148-1).
Table 148-1 Disorders Categorized as Non-Langerhans Cell Histiocytosis (with Abbreviations) ||Download (.pdf)
Table 148-1 Disorders Categorized as Non-Langerhans Cell Histiocytosis (with Abbreviations)
Juvenile xanthogranuloma (JXG)
Generalized eruptive histiocytosis (GEH)
- Benign cephalic histiocytosis (BCH)
Xanthoma disseminatum (XD)
- Erdheim–Chester disease (ECD)
Multicentric reticulohistiocytosis (MRH)
- Solitary cutaneous reticulohistiocytosis (SRH)
- Diffuse cutaneous reticulohistiocytosis (DRH)
Progressive nodular histiocytosis (PNH)
Necrobiotic xanthogranuloma (NXG)
Sinus histiocytosis with massive lymphadenopathy (SHML)
In some textbooks, these diseases are gathered under the term: macrophage/dermal dendritic cell disorders. In 2001, Zelger et al suggested a unifying approach to understand this disease group. They identified different types of macrophages in the prototype lesion, juvenile xanthogranuloma, and then used this morphology to subcategorize the diseases.
Clinicopathologic overlap makes it difficult to place some patients exactly into one defined entity, indicating a close relationship between these disorders. While many of these disorders may feature foamy cells, affected patients are normolipemic. In all instances, the etiology and pathogenesis are unknown.1
Most of these cells share the same immunophenotypes, but the resulting disorders differ in clinical presentation and course. Although all NLCH disorders are considered reactive with no clinical evidence of malignancy, some forms, as with class I histiocytosis (Langerhans cell histiocytosis or LCH), can be invasive and therefore they are not necessarily biologically benign. Patients have been described who have developed both LCH and an NLCH, particularly, juvenile xanthogranuloma (JXG).
These cases seem to demonstrate a relationship between LCH and NLCH.2 According to some authors the dendritic cell is the presumed cell of origin of both LCH and NLCH, leading to the shared categorization of these diseases as dendritic cell-related disorders and separated from macrophage-related proliferations such as sinus histiocytosis with massive lymphadenopathy (SHML), ...