Page 1264 - Cote clinical veterinary advisor dogs and cats 4th

634 Mast Cell Tumors, Dog

• Surgery is the primary treatment modality. q 12-24h or diphenhydramine 1-2 mg/ Chemotherapy or targeted therapy is recom-
Exploratory laparotomy/GI mass resection kg PO (most cats dislike the taste of the mended for these cats after surgery.
VetBooks.ir biopsies, even if the tissue appears normal, Cyproheptadine is recommended for feline PEARLS & CONSIDERATIONS
liquid suspension) or SQ (anecdotal) q 12h.
with liver and mesenteric lymph node
are indicated.
MCT due to its antiserotonin properties
• Splenectomy is the treatment of choice in
cats with splenic MCTs, even if metastasis and ease of administration compared with Comments
diphenhydramine (side effects may include
Many cats with mast cell disease develop
or cutaneous MCT is present. After appetite stimulation). Proton pump inhibi- additional MCTs, including cutaneous, splenic,
splenectomy, disseminated disease may tors or H2 blockers should also be used in and GI forms. Patients should be rechecked
improve spontaneously and/or respond to cats with measurable MCT. at least q 4-6 months by physical exams and
chemotherapy or targeted therapy. • Supportive care, including nutritional and possibly with restaging. The prognosis for feline
Chemotherapy and targeted therapy: blood product support and analgesia, is MCTs varies widely, and individual cases should
• Potential indications: multiple or recurrent indicated perioperatively as needed. be discussed with an oncologist to devise an
cutaneous MCTs, metastasis at diagnosis, or appropriate diagnostic/therapeutic plan and
before attempting surgical excision of large, PROGNOSIS & OUTCOME likely prognosis.
infiltrative tumors.
• CCNU (lomustine) in cats with measur- • The prognosis for cats with solitary cutaneous Technician Tips
able MCT has a response rate of 50%, MCTs is good, and recurrence after excision In cats, MCTs are often located on the head
with a median duration of response of 168 or RT is uncommon. Cutaneous MCTs with and neck and have a white-to-pink pimplelike
days. > 5 mitoses/10 HPF have a worse prognosis. appearance. They may not change in appearance
• Other drugs that may be effective include No factors are known to be predictive for for years and are often overlooked. Aspiration
prednisone, chlorambucil, and vinblastine. development of multiple cutaneous MCTs, cytology is diagnostic in most cases. In cats,
Special handling requirements and potentially regional lymph node metastasis, or splenic clipping the fur (even the entire haircoat) may
severe or life-threatening adverse patient or visceral MCTs. be indicated to identify all MCTs because they
effects exist with these chemotherapeutic • Cats with multiple cutaneous MCTs or are often so small, but make sure to obtain
drugs; these concerns and rapid evolution of cats with cutaneous tumors plus distant owner permission.
protocols warrant consultation with/referral metastases have a median survival time
to an oncologist. of 582 days; longer median survival times Client Education
• Drugs that inhibit tyrosine kinase recep- are reached by cats with solitary dermal Client education about the pimplelike, small
tors (toceranib [Palladia]) may be used in MCTs and by cats with cutaneous MCTs size of most feline MCTs is essential because
conjunction with or instead of chemotherapy compared with cats that have splenic or early diagnosis and therapy are most likely to
(3/14 cats that failed other treatments had visceral tumors. result in successful treatment. Any new skin
partial or complete responses to Palladia), • Prognosis for cats with solitary splenic MCTs: mass or signs of illness should be evaluated as
Consultation with an oncologist is advised median survival time after splenectomy is soon as possible.
before use. ≈4-28 months. With involvement of addi-
Adjunctive therapies: tional sites (liver, skin), the prognosis varies, SUGGESTED READING
• Intralesional corticosteroids and de-ionized and chemotherapy or toceranib should be Sabbatini S, et al: Prognostic value of histologic and
water are rarely useful and are not advised. considered. immunohistochemical features in feline cutaneous
• Antihistamines are indicated for cats with • Primary GI MCTs have the poorest prog- mast cell tumors. Vet Pathol 47(4):643-653, 2010.
MCTs before surgical excision or in cases nosis (many cats die perioperatively or in AUTHOR: Tracy Gieger, DVM, DACVIM, DACVR
of nonresectable or metastatic disease. 2-3 months postoperatively), which may EDITOR: Kenneth M. Rassnick, DVM, DACVIM
Consider cyproheptadine 2 mg/CAT PO improve if the lesions are surgically resectable.

Mast Cell Tumors, Dog Client Education
Sheet

Epidemiology Clinical Presentation
BASIC INFORMATION
SPECIES, AGE, SEX HISTORY, CHIEF COMPLAINT
Definition Can occur in any age dog; the median age in • Most dogs show no clinical signs and are
Canine mast cell tumors (MCTs) are neoplastic dogs is 8 years. evaluated for an incidentally discovered cuta-
accumulations of mast cells. MCTs produce del- neous or subcutaneous mass. Lesions might
eterious effects when the mast cells degranulate, GENETICS, BREED PREDISPOSITION be pruritic or have a history of shrinking and
releasing bioactive substances that can produce Breeds predisposed to MCT include boxer, swelling. MCTs often remain unchanged in
cutaneous or systemic effects, depending on Boston terrier, golden retriever, Labrador size for months before presentation or may
location. In dogs, cutaneous and subcutaneous retriever, pug, Shar-pei, Staffordshire bull terrier, be rapidly growing.
MCTs are common, and extracutaneous MCTs Jack Russell terrier • Occasionally, dogs are evaluated because of
are uncommon. signs related to gastric ulceration (vomit-
ASSOCIATED DISORDERS ing, diarrhea, weight loss, melena) sec-
Synonyms Caused by mast cell degranulation: gastro- ondary to histamine-induced gastric acid
Mastocytoma, systemic mastocytosis (metastatic intestinal ulceration, pruritus, hypotension, secretion.
MCT) and delayed wound healing

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