Mast cell tumors Flashcards
How do mast cell tumors occur in cats
Mast cell tumors occur in three main forms in cats:
- cutaneous
- intestinal (the third most common type of cancer in the GI system of cats after lymphoma and adenocarcinoma)
- visceral (which may or may not have skin metastases) (most common splenic disease in cats)
What is the relative prevalence of the different mast cell tumors
Intestinal (5% of cases) and visceral (20% of cases) forms of MCT are much less common than the cutaneous form (75% of cases)
What are the typical clinical signs of visceral /splenic MCT
The most common presenting clinical signs are:
- anorexia
- lethargy
- persistent or intermittent vomiting
- splenomegaly
What is the treatment of choice for visceral MCT
The treatment of choice for visceral MCT is splenectomy
- even in the presence of other visceral involvement, this is a valuable procedure, and can lead to improvement in other signs (e.g., resolution of vomiting and circulating mast cells)
Pre-treatment with glucocorticoids, antihistamines (H1 and H2 blockers) and a serotonin anatgonist (e.g., cyproheptadine) for 48 hours prior to surgery are recommended
How frequent are mast cell tumors in cats
Mast cell tumors account for up to 15% of all tumors in cats
- they have been reported as the third most frequent tumor in cats after lymphoid and mammary neoplasms
Cutaneous MCTs are the second most common skin tumors in cats in the USA
What is the specificity of mast celles when compared to other white blood cells
Similar to other leukocytes, mast cells derive from pluripotent hematopoietic stem cells of the bone marrow
Unlike other leukocytes, these cells leave the bone marrow as precursor cells and differentiate to mature mast cells in connective tissue or mucosa, while retaining the capacity to proliferate
What is the c-Kit proto-oncogene
The c-Kit proto-oncogene encodes a receptor tyrosine kinase that is a transmembrane receptor that consists of five immunoglobulin-like domains extracellularly, a transmembrane domain, and an intracellular domain that includes the juxtamembrane and kinase domains
What is the mean age and clinical presentation of cutaneous MCT
Mean age of 8-10 years
Cutaneous MCTs appear as a firm, well-circumscribed, hairless, dermal nodule, that may or may not be ulcerated, and generally range in size from 0.2 to 3 cm
The tumors are more generally solitary nodules
- but 20% of cats have multiple cutaneous tumors
What are the main locations for cutaneous MCTs
The head and neck are the most commonly affected locations in the cat
What are the two histologically groups of feline cutaneous MCTs
Feline cutaneous MCTs are classified histologically into two groups:
- mastocytic which is subcategorized as well-differentiated (the most common) and pleomorphic (tend to infiltrate more deeply into the subcutis and have more eosinophilic infiltration)
- atypical (formerly known as histiocytic-type MCTs) (rare). More commonly seen in cats younger than 4 years of age
What are the prognostic factors for cutaneous MCTs in cats
Cats with solitary MCTs tend to have a more favorable outcome than those with multiple cutaneous MCTs
Mitotic index is the only prognostic factor that is generally agreed upon
- high grade >5 mitotic figures per 10 HPF
Explain why the buffy coat examination is important in the diagnostic work up of a suspected splenic MCT
All cats with splenic MCT had mastocytemia in one study
