Overview of Histiocytic Diseases - Public Version
The clinical presentation and behavior and responsiveness to therapy vary tremendously between the various histiocytic disease syndromes. Canine cutaneous histiocytoma is a benign neoplasm which usually occurs as a single lesion in young dogs of all breeds, and spontaneously regresses (there are rare exceptions to this rule).
Cutaneous Langerhans cell histiocytosis (LCH) covers a spectrum of disease, in which multiple cutaneous histiocytomas are observed. Lesions may spontaneously regress or progress with the potential for systemic spread.
Cutaneous histiocytosis (CH) presents with single or multiple lesions, which tend to wax and wane, and may even spontaneously regress. A few cases respond to corticosteroids, the remainder persist and may require more aggressive immunosuppressive therapy.
Systemic histiocytosis (SH) is a familial disease of Bernese Mountain Dogs and also occurs sporadically in other breeds. SH presents with prominent skin manifestations identical to those seen in CH, but mucous membranes (ocular and nasal) and a variety of other organ systems, including lymphoid organs, lung, and bone marrow may also be involved. Although the lesions may wax and wane early in the course, SH is a progressive disease that often requires continuous immunosuppressive therapy.
Histiocytic sarcomas (HS) (formerly malignant histiocytosis - MH) occur with high incidence in Bernese Mountain Dogs, Rottweilers, Flat Coated Retrievers, Golden Retrievers and sporadically in many other breeds. Histiocytic sarcomas occur as localized lesions in spleen, lymph nodes, lung, bone marrow, skin and subcutis, brain, and periarticular tissue of large appendicular (limb) joints. Histiocytic sarcomas can also occur as multiple lesions in single organs (especially spleen), and rapidly disseminate to involve multiple organs. Hence, disseminated histiocytic sarcomas are diﬃcult to distinguish from MH, which is a multi‐system, rapidly progressive disease in which there is simultaneous involvement of multiple organs such as spleen, lymph nodes, lung, bone marrow, skin and subcutis. Hence, disseminated HS has now replaced MH in the literature. Response of histiocytic sarcomas to chemotherapy is often brief.