Page 967 - Cote clinical veterinary advisor dogs and cats 4th

Histiocytic Diseases 475

Chronic Treatment • Three-view thoracic radiographs and physical diagnosing DC-origin disorders and ruling
• Reactive histiocytoses are typically treated exam, including lymph node palpation and out lymphoma. Polymerase chain reaction
VetBooks.ir prednisone 2 mg/kg PO q 24h is used until 3 months for the first year after diagnosis (PARR) may not adequately distinguish Diseases and Disorders
with immunosuppressive therapy. Initially,
(PCR) for antigen receptor rearrangement
exam of the site, should be performed every
HS from lymphoma because of infiltrating
clinical response is noted; then a slow taper
for localized HS and every 4-6 months
of 1 mg/kg PO q 24h for 1 month, 0.5 mg/
clonal T cells in HS.
kg PO q 24h for 1 month, 0.5 mg/kg PO q thereafter. ○ Newer markers include ionized calcium
48h for 3 months, and then stop or maintain PROGNOSIS & OUTCOME binding adaptor molecule 1 (IBA-1) with
at lowest effective dose. good sensitivity and specificity and CD204
• If no response is noted within 1 month of • CH: good; may regress spontaneously or with conflicting reports of utility.
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prednisone therapy or lesions relapse and no respond to immunosuppressive doses of ○ Dendritic cells should be CD1a or CD1c ,
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longer respond to prednisone, azathioprine prednisone CD11c , and MHC II (Langerhans DCs
2 mg/kg PO q 24h, with the same taper • SH and disseminated HS: poor. SH may are associated with E-cadherin positivity
schedule as prednisone or cyclosporine may wax and wane but is ultimately progres- as in most histiocytomas, and interstitial
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be added. sive, whereas disseminated HS is rapidly DCs are CD90 )
• Evidence suggests efficacy of tetracycline and progressive, with both leading to death. ○ Macrophages (hemophagocytic HS) should
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niacinamide (dogs < 10 kg: 250 mg of each Disseminated HS is considered uniformly be CD 1 low/− , CD11c , and CD11d as
drug PO q 8h, and dogs > 10 kg: 500 mg fatal. Survival of dogs with SH ranges from well as lysozyme positive.
of each drug PO q 8h). months to years. Survival for dogs with dis- ○ Malignant histiocytic diseases should be
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• All treatments can be used with or without seminated HS averages 4 months, although CD4 , and reactive syndromes, CD4 .
antibiotics, depending on appearance of skin chemotherapy in the adjuvant setting with
lesions and at the discretion of the treating CCNU may prolong survival to greater than Prevention
clinician. 1 year for some dogs (see Treatment above). Because histiocytic diseases are often inherited,
• Systemic malignant histiocytic diseases are Prognosis to date for cats with malignant careful documentation of pedigrees for affected
poorly responsive to therapy, and remissions, histiocytosis is similarly grave, and response animals may reduce disease through selective
if achieved, are typically short lived. to therapy has been poor. breeding. Inheritance of histiocytosis in BMDs
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○ CCNU 60-90 mg/m (p. 609); 29%-46% • Focal histiocytic sarcoma: good if low grade has been calculated at a moderate 0.298, sug-
response with macroscopic disease. Dogs and local control is achieved with surgery gesting that careful breeding could be effective
with metastasis limited to lymph nodes ± radiation therapy. Periarticular HS has a at eliminating this disease. This means that
responded favorably (median survival time, better prognosis than that at other sites, 29.8% of the risk of developing histiocytosis
219 days; 38% 1-year survival). CCNU even with suspected metastasis at the time in the population of BMDs is attributable
has been used in combination with other of diagnosis. CNS HS has a grave prognosis to genetic differences among individuals.
drugs with similar results. (3 days). The remainder of the risk is environmental,
○ Other chemotherapy drugs that have • More than 1 of 7 BMDs and FCRs die from although specific factors have not been
been used include doxorubicin 30 mg/ HS. identified.
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m IV (p. 609), epirubicin 30 mg/m IV
(p. 609), and dacarbazine 900-1000 mg/ PEARLS & CONSIDERATIONS Technician Tips
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m (p. 609) diluted in saline over 5 Some tumor-bearing dogs have coagulopathies.
hours, although none provided durable Comments Although peripheral veins may be preferred for
responses. The following clinical and pathologic differences routine blood draws, they may be needed to
○ Liposome-encapsulated clodronate, a novel can help differentiate histiocytic syndromes: deliver intravenous chemotherapy.
formulation of a bisphosphonate capable • Clinical findings/behavior
of eliminating macrophage/dendritic ○ Disseminated HS is a multiorgan disease Client Education
cells, is not widely available but has been typically arising from internal sites, includ- • Owners should contact the breeder or source
reported and may be useful in treatment. ing viscera, whereas SH involves skin and of affected animals.
○ TALL104 (cytotoxic T lymphocytes) lymph nodes with occasional internal sites. • An overtly (phenotypically) normal breeding
therapy has been described but is not ○ CH is limited to the skin and does not pair of BMDs with one affected offspring
commercially available. lead to HS. will produce on average one in seven puppies
• Focal malignant histiocytic diseases respond ○ Hemophagocytic HS may be confused that will ultimately succumb to histiocytosis.
well to surgical resection (amputation if joint with Evans syndrome (anemia and
or bone affected or complete resection with thrombocytopenia), but HS is Coombs SUGGESTED READING
limb salvage impossible) ± irradiation. negative. Moore PF: A review of histiocytic diseases of dogs
• Histopathology and immunohistochemistry and cats. Vet Pathol 51(1):167-184, 2014.
Recommended Monitoring for dogs and cats
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• The involved site(s) should be monitored ○ CD18 (leukocyte marker), CD3 , and AUTHOR: Kim A. Selting, DVM, MS, DACVIM, DACVR
EDITOR: Kenneth M. Rassnick, DVM, DACVIM
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closely by regular observation and diagnostic CD79a are three stains and the immu-
imaging as appropriate. nohistochemical pattern most useful for

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