Small Animal Dermatology, 3rd edition

CHAPTER 25 HISTIOCYTIC PROLIFERATIVE DISORDERS 381

 Reactive systemic histiocytosis:
Dysregulation of dendritic “antigen-presenting” cells producing a reactive

perivascular proliferation

Slowly progressive disease.

 Familial disease of Bernese mountain dogs:
Polygenic mode of inheritance
Heritability of 0.298; accounts for up to 25% of all tumors in this breed
Characterized by multiple cutaneous, ocular, and nasal mucosa nodules
Other organ systems (lung, spleen, liver, bone marrow) may also be affected.

 Histiocytic sarcoma (localized histiocytic sarcoma, disseminated histiocytic sarcoma,

malignant histiocytosis):

Malignant transformation of dendritic cells

Rapidly progressive, multisystem disease

Disease affects the skin (nodules) and subcutis, spleen, lymph nodes, lung, bone

marrow

Usually leads to death in a matter of weeks.

 Malignant fibrous histiocytoma:
Uncommon in cats; rare in dogs
Solitary, firm, poorly circumscribed soft tissue sarcomas.

SIGNALMENT/HISTORY

 Cutaneous histiocytoma:
Young dogs; most under 3 years of age
Breeds predisposed: bull terrier, Boston terrier, boxer, Shetland sheepdog,

dachshund, cocker spaniel, Great Dane.

 Reactive cutaneous histiocytosis:
Middle-aged to older dogs; range 2–13 years
Possible male predisposition
Breeds predisposed: Bernese mountain dog, beagle, collie, golden retriever, and

Shetland sheepdog.

 Reactive systemic histiocytosis:
Young adult to middle-aged dogs; mean age at onset 4 years
Male predisposition
Polygenic mode of inheritance in Bernese mountain dog
Breeds predisposed: rottweiler, basset hound, Irish wolfhound, golden retriever,

and Labrador retriever.

 Histiocytic sarcoma complex:
Older male dogs; mean age at onset 7 years
Most common in Bernese mountain dog
Breeds predisposed: Labrador retriever, rottweiler, golden retriever, and flat-

coated retriever.

 Malignant fibrous histiocytoma:
Uncommon (cats); rare (dogs)
Middle-aged to older cats.