Treatment options for canine cutaneous mast cell tumors
You'll likely encounter patients with these neoplasms in your practice. Luckily, many treatment options are available, such as surgery, radiation therapy, and chemotherapy—and new treatments are on the horizon.
FIGURE 1. A large pedunculated cutaneous mast cell tumor on a mixed-breed female dog. This mass was assumed to be benign
until cytologic and histopathologic diagnosis of mast cell disease was confirmed three years after being first noticed. FIGURE
2. Shar-Peis are reported to have more aggressive and invasive mast cell tumors. This female Shar-Pei had diffuse infiltrative
mast cell disease originating from the medial aspect of the left hindlimb, with rapid involvement of the mammary tissues.
FIGURE 3. A hyperpigmented raised lesion involving the left lateral thigh region. Given the anatomical location, complete
surgical excision with wide margins was obtained, providing a local cure for this dogs grade II mast cell tumor. FIGURE 4.
A raised erythematous mucocutaneous lesion involving the preputial orifice on a castrated male pug. The mass was surgically
excised and confirmed to be a grade II mast cell tumor.
Canine mast cell tumors are the most frequently diagnosed malignant skin neoplasms in dogs.1 Although they often appear as raised, erythematous, alopecic masses, mast cell tumors can adopt various benign or aggressive
clinical presentations, as well as involve different anatomical sites (Figures 1-4). While dogs of any breed can develop mast cell tumors, overrepresented breeds include boxers, bulldogs, Boston terriers,
Weimaraners, golden and Labrador retrievers, and Shar-Peis.2,3 Because you will likely encounter canine cutaneous mast cell tumors in your practice, this review article focuses on summarizing
the therapeutic options available for treating canine mast cell tumors. With a better understanding of available treatment
regimens, you will be able to educate and guide pet owners regarding the treatment options that may best suit their dogs.
BIOLOGIC BEHAVIOR AND CLINICAL STAGE
TABLE 1. Accepted Histologic Grading System for Cutaneous Canine Mast Cell Tumors
Before instituting the most appropriate therapy, it is important to understand that treatment options are based on the predicted
biologic behavior, as well as the extent of disease associated with canine mast cell tumors. Histologic grade has been shown
to be the most important prognostic factor for predicting biologic behavior and survival times in dogs with mast cell tumors.2 Currently in dogs, mast cell tumors are histologically categorized into grades I, II, and III (Table 1). With surgical resection only, the percentages of dogs surviving 1,500 days after diagnosis have been reported to be 83%,
44%, and 6% for grades I, II, and III tumors, respectively.2 Grade I mast cell tumors tend to be locally confined to the skin and nonmetastatic. Grade II mast cell tumors are generally
local, but some can be aggressive with regional node and distant organ metastasis. Grade III mast cell tumors tend to be biologically
aggressive, possessing a high propensity for regional and distant metastasis. Although histologic grade remains the gold standard
for predicting the biologic behavior of cutaneous mast cell tumors, other prognostic factors include tumor location, proliferative
indices, breed, recurrence, c-kit mutations, c-kit staining pattern, and microvessel density.4-11