Small Animal Dermatology, 3rd edition

CHAPTER 25 HISTIOCYTIC PROLIFERATIVE DISORDERS 387

lymphopenia and anemia are uncommon side effects; most common side effect is

vomiting

Azathioprine: 2 mg/kg or 50 mg/m2 PO q24h until remission; then EOD or twice

weekly.

 Histiocytic sarcoma (malignant histiocytosis):
Typically nonresponsive
Rapidly progressive, and fatal
Fails to respond to therapy
Chemotherapy often trialed including corticosteroids, cyclophosphamide, vin-

cristine, and doxorubicin-based protocols

Fluid therapy or blood transfusions may be required depending on clinical

findings.

 Malignant fibrous histiocytoma:
Surgical excision if possible
Poor prognosis due to local invasion and tendency to metastasize.

COMMENTS

 Effectiveness of treatment is determined by repeated physical examinations, CBC and

biochemistry profiles, and diagnostic imaging.

 Patients with systemic disorder have a fluctuating debilitating disease that can be

characterized by multiple clinical episodes and asymptomatic periods.

 Prognosis for malignant disorder is extremely poor; death usually occurs within a few

months of diagnosis.

Fig. 25.1.Multiple cutaneous histiocytomas in a 2-year-old male-castrate Chinese shar pei. Additional nod-
ules were noted over most of the body.