Mast cell tumors in cats: clinical update and possible new treatment avenues

Abstract

Practical relevance: Feline mast cell tumors (MCTs) are frequently encountered in general practice. MCTs are the most common splenic tumor, second most common skin tumor and third most common intestinal tumor in cats. Treatment and prognosis can vary dramatically with location and histologic classification.

Clinical challenges: While a cytologic or histologic diagnosis is often easy to obtain, the various histologic classifications, lack of a relevant grading scheme, and disparity in behavior depending on anatomic location make prognostication for cases of feline MCTs confusing. This is quite different from canine MCTs, where there is an established grading system which correlates clinically with prognosis and an accepted standard of care.

Audience: Due to its prevalence, general practitioners encounter MCTs regularly. In many instances, referral for diagnosis and treatment is not necessary.

Evidence base: Historically, there has been limited clinical evidence upon which to determine optimal treatment of MCTs in cats. Most recommendations are based on limited case reports or retrospective studies. With the recent introduction of receptor tyrosine kinase inhibitors to the veterinary market, there has been new research on the use of these drugs in cats, and new treatment options are on the horizon.

Figure 1

A 1.5-year-old domestic longhair cat with a solitary cutaneous MCT evident on the lower lip. Lymph node metastasis was detected and this cat developed diffuse skin lesions and circulating mast cells. Courtesy of Dr Sarah Kraiza

Figure 2

MCT affecting the lateral canthus. Periocular MCT may be associated with a lower recurrence rate than MCTs at other sites, although tumor size and location may limit surgical options. Courtesy of Dr Elizabeth Giuliano, University of Missouri

Figure 3

Diffuse distribution of poorly differentiated MCT affecting the head, neck and trunk. Courtesy of Dr Andrew Novosad

Figure 4

Enlarged, mottled spleen of a cat with splenic MCTs. Courtesy of Cuyahoga Falls Veterinary Clinic (fallsvetclinic.com)

Figure 5

Cytological preparation typical of feline MCT, with cytoplasmic granules easily identified. Courtesy of Dr Marlyn Whitney, University of Missouri

Joey at initial presentation

Cytology from a fine-needle aspirate of a cutaneous lesion

Joey at recheck evaluation, with more diffuse distribution of lesions

Cytological preparation of splenic aspirate, x1000. Courtesy of Dr Autumn Dutelle and Dr Sara Hill; BluePearl Veterinary Partners, Eden Prairie, MN, USA