Mast Cell Tumors Flashcards
What is the most common cutaneous tumor in dogs and cats?
Dog : mast cell
Cat : basal cell tumor > mast cell
The systemic form of mast cell tumors are called??
Mastocytosis
Breeds predisposed to mast cell tumors?
Dog: boxer, bull terrier, boston terrier, and bulldog
Cat: Siamese
Mean age of presentation with mast cell tumors?
8-9yrs in both cats and dogs
T/F: Boxers are predisposed to mast cell tumors and tend to have vary aggressive variants
False
Tend to have lower grade/less aggressive variants
Cutaneous MCT tend to be in what location on the body?
Cats: head and neck
Dog: trunk > extremities> head/heck
Can also be found in oral cavity, larynx, trachea, mediastinum, GI tract, and nasopharynx
Mast cells are composed of cytoplasmic granules which contain which substances??
Vasoactive - histamine, prostaglandins
Heparin-proteoglycan
Chemotactic factors
Proteolytic enzymes
Serotonin
A disturbance of a mast cell tumor can lead to Darier’s sign which appears how?
Erythema, swelling
If severe.. anaphylaxis and hypotension
How do mast cell tumors lead to GI ulcers?
Histamine stimulates H2 receptors on gastric parietal cells = increase gastric acid secretion
Plasma histamine levels = initially increase in dog with gross MCT and progressively increase in dog with poor tumor control and MCT-associated GI signs
Histamine damages gastric submucosal vasculature —> small venue and capillary dilation, increased endothelial permeability and results in intravascular thrombosis, decreased gastric blood flow, and ischemic necrosis of mucosa
How do you control degranulation from MCT?
Premed with H1 antagonsit to prevent platelet degranulation, anaphylaxis, and hypotension during handling
Management with H1 and H2 antagonist during interval from diagnosis to tx or from tx time until confirmation of local dz
Long term usage with systemic dz
What effect does degranulation have on surgery?
Delayed wound healing
-local effects of proteolytic enzymes and vasoactive amines
Hypotension
- histamine and other vasoactive amines
Local hemorrhage
-heparin release from MCT
T/F: surgical dehiscence is a common problem with mast cell tumors
True
Work up and staging of MCT?
MDB
Regional LN aspirated
—> only tests if no neg prognostic indicators present
Abdominal ultrasound and bone marrow aspiration if negative risk factors present
T/F: MCT commonly met to lungs
False
They do NOT met to lungs
Stage the MCT..
1 incompletely excised cutaneous MCT
Stage 0
Stage the MCT
1 cutaneous MCT
Stage 1
Stage the MCT..
1 cutaneous MCT with regional lymph node met
Stage 2
Stage the MCT..
Multiple MCT or a large infiltrative MCT with or without LN mets
Stage 3
Stage the MCT..
Any MCT with distant mets for BM involvement
Stage 4
What are the two distinct types of MCT in cats ?
Mastocytic (more common) - histologically simile to dogs
Histiocytic - characterized by histiocytic-like MC
What is the therapy and prognosis for mastocytic MCT?
Surgical excision (doesn’t require wide excision)
Splenic/Visceral MCT - Good prognosis with splenectomy
Intestinal MCT - poor prognosis
What is the prognosis and therapy for a histiocytic MCT in a cat?
Good prognosis
- treatment is to wait and see because they can spontaneously regress over 4-24months
How are MCT graded?
Well, moderately, poorly differenated - based on the amount of cytoplasmic granules, degree of anisocytosis, anisokaryosis, and nuclear:cytoplasmic ratio
Kiupel system= more simple, objective and based solely on cellular features that could be evaluated cytologically
What is the treatment of a cutaneous MCT?
Localized - wide excision (2-3cm with deep fascial plane )
—> complete excision/low grade - DONE
—> complete excision/high-grade - adjunct chemo
Localized non-respectable
—> RT alone control 50% for 1yr
—> chemo to down stage then surgery
—>chemo alone control 64% but short lived
What do you do if you remove a MCT but have incomplete margins ?
Scar revision
Surveillance —> only 20-30% recurred (not ideal for high grade variants)
RT - 2yr control rate of 85-95%
Chemo
How do you treat disseminated disease with a local tumor?
Adjunctive chemo in combo with surgery/RT to control bulky disease
What chemotherapy is given for MCT?
Pre/vinblastine MST 3.8yrs
Cyclophosphamide/VBL for microscopic residual dz : MST. 5.8yrs
T/F: Tyrosine kinase inhibitors should be used in all MCT cases because they all express KIT genes
False
They all express KIT genes but only 20-40% have the c-KIT mutation -> prognostic panel tests for mutation to see if TKI would be useful in treatment
What are the patient related prognostic factors for MCT?
Breed - boxers and other brachycephalic tend to have less aggressive variants
Systemic signs - associated with higher stage
Location- worse prog if subungual, oral or other mm’s, preputial and scrotal, visceral or BM. SQ do better.
Stage= higher stage worse
What are tumor related prognosis factors for MCT?
**Size - greater than 5cm have worse survivial
Growth rate/time tumor present
- slow growth = less aggressive
**Molecular markers - ckit = worse
**Proliferation rate
Microvessel density - increased = high grade
- *Recurrence
- *Histologic grade - strong predictor of outcome
T/F: multiple tumors is a negative prognostic factor for MCT
False
Many studies show that outcome of multiple tumors is similar to single MCT if adequate treatment initiated for each mass
