Exam 2 - Mast Cell Tumors Flashcards
what is the most common skin tumor in the dog?
mast cell - 16-21% of all skin tumors
what breeds are predisposed to mast cell tumors?
brachycephalic breeds, labs, beagles, & schnauzers
what is the average age of an animal affected by a mast cell tumor?
9 years old - but can be seen in dogs as young as 3 weeks old
what are the 3 forms of mast cell tumors in dogs?
- dermal form
- visceral form
- intestinal form
what are the clinical signs of dermal mast cell tumors in dogs?
variable signs
release of bioactive constituents result in - gi ulcers, hypotension, coagulation abnormalities, & delayed wound healing
solitary vs. multiple masses
what is darier’s sign?
local reaction seen when a mast cell tumor degranulates
urticaria, erythema, hives, & edema
what is shown here?
dermal MCT showing darier’s sign - urticaria, edema, erythema, & hives
where do MCT almost never metastasize to?
the lungs
what are the common sites of metastasis of mast cell tumors?
lymph nodes, spleen, liver, & bone marrow
what is the prognosis of a low grade mast cell tumor? what is the rate of metastasis seen?
MST > 2 years
<18% metastatic rate
what is the prognosis of a high grade mast cell tumor? what is the rate of metastasis seen?
MST < 4 months
metastatic rate >70%
what are the characteristics that signify a high grade mast cell tumor?
mitotic index >/= 7
> 3 multinucleate cells in 10 HPF
> 3 bizarre nuclei in 10 HPF
karyomegaly - abnormally enlarged cell nucleus, at least 10% of cells that have a 2 fold increase in size to qualify for this
what is the 2 tier grading system of mast cell tumors? what does it apply to?
only applies to cutaneous MST - 96.8% consistency & 99.3% agreement
broken up into low grade (90% of tumors we see are considered to be low grade) & high grade
using WHO staging, what is a stage 0 MCT?
1 tumor that is incompletely excised from the dermis, identified histologically without regional lymph node involvement
0a - no systemic signs
0b - systemic signs present
using WHO staging, what is a stage I MCT?
1 tumor confined to the dermis without regional lymph node involvement
1a - no systemic signs
1b - systemic signs present
using WHO staging, what is a stage II MCT?
1 tumor confined to the dermis with regional lymph node involvement
IIa - no systemic signs
IIb - systemic signs present
using WHO staging, what is a stage III MCT?
multiple dermal tumors
large, infiltrating tumors with or without regional lymph node involvement
IIIa - no systemic signs
IIIb - systemic signs present
using WHO staging, what is a stage IV MCT?
any tumor with distant metastasis including blood or bone marrow involvement
how are cutaneous MCT diagnosed?
FNA - often bleed & swell
biopsy - pre-medicate the animal with benadryl, famotidine, +/- steroids to avoid side effects of histamine release
IHC
what special stains are used for diagnosing MCT?
wright stain commonly used
t-blue, vimentin, a-1-antitrypsin, & CD117 (c-kit)
what is the mast cell tumor prognostic panel? what is included?
a panel of factors known to help predict MCT behavior - has to be done on biopsied tissue
Ki67, AgNOR, c-kit (staining pattern & PCR for mutations)
c-kit - will tell you how much you have on the surface, but doesn’t tell you if it is mutated!!!!
what staging is used for MCT?
bloodwork - cbc, chemistry, & UA
regional lymph node aspirates
chest rads
abdominal ultrasound
what are some prognostic factors evaluated for MCT?
histological grade - best predictor for dermal tumors!!!!!
clinical stage
location - mucocutaneous junctions are worse
cell proliferation
growth rate
recurrence - always will come back more aggressive than the first time
systemic signs - indicates more severe disease/stage
breed of the animal - boxers tend to get low grade MCT & labs tend to get high grade MCT
c-kit mutation - exxon 11 mutations have a worse prognosis vs no mutations or exxon 8 mutation
tumor size - bigger the tumor, the harder it is to get local control
how is surgery used to treat cutaneous MCT?
premedicate the animal - diphenhydramine & steroids
get 2-3cm margins & 1 fascial plane deep - look for enlarged lymph nodes
may use cytoreduction or amputation
when is radiation therapy used for cutaneous MCT?
only in microscopic disease!!!!!!!! worried about massive anaphylactic reaction due to mass degranulation of tumor, so used after surgery to clean up margins
definitive therapy with 85-95% cure rate for grade I tumors & 50% 1 year control rate for grade III tumors
what long term radiation effects are seen in animals with cutaneous MCT?
depigmentation at most intense site of treatment, hyperpigmentation around the general area, alopecia, & hair changes colors in the areas that received the least amount of radiation
what chemo drug will you never use for an animal with cutaneous MCT? why?
doxorubicin - main side effect is mast cell degranulation causing a hypersensitivity like reaction
when is chemo used for MCT? what drugs can be used?
high grade tumors, microscopic setting after surgical removal, & non-resectable tumors
vinblastine (blasts mast cells, #1 drug), lomustine, cyclophosphamide, & chlorambucil - use all concurrently with prednisone!!!!
all drugs here are cytotoxic - will kill cells, always start with a cytotoxic drug
how does torceranib phosphate (palladia) work for treating cutaneous MCT? what are some side effects associated with it?
good class of drug for treating MCT with c-kit mutations - receptor tyrosine kinase inhibitor that inhibits VEGF, PDGFR, c-kit, & FGFR
gi ulcers, muscle pain, neutropenia, thrombocytopenia, & proteinuria
how does masitinib mesylate (kinavet) work for treating cutaneous MCT? what are some side effects associated with it?
receptor tyrosine kinase inhibitor that inhibits PDGFR, c-kit, & mutated FGFR
gi ulceration, neutropenia, & proteinuria
what are some treatment options for ancillary therapy for a patient with MCT?
diphenhydramine, h-2 blockers, sucralfate, pain meds, & protamine
what is the MST for intestinal mast cell tumors in dogs & cats with aggressive therapy? why?
<120 days - very aggressive tumor type with a very high metastatic rate
what treatment is recommended for intestinal mast cell tumors in dogs & cats?
surgical removal with 10cm margins & always followed with chemotherapy
what is the visceral form of MCT in cats?
spleen, liver, lymph nodes, & bone marrow are involved
what is the cutaneous form of MCT in cats?
of the dermis - head & neck, non-haired areas, fleshy, & often in multiples
what cat breed/signalment is predisposed to cutaneous MCT?
young male siamese cats
what is the 2nd most common skin tumor in cats?
cutaneous mast cell tumor - makes up 20% of all skin tumors
what is the typical age of a cat seen with a mastocytic cutaneous MCT?
10 years old - similar to MCT found in dogs
what is the typical age of a cat seen with a histiocytic cutaneous MCT?
young cats - 2.4 years old, histiocytic mast cells that act like histiocytomas in dogs, look like eosinophilic plaques
need to do a biopsy to differentiate mast cell tumor from rodent ulcer
T/F: cats rarely show systemic signs with cutaneous MCT
true
what are some clinical signs associated with visceral MCT in cats?
weight loss, anorexia, diarrhea, melena, vomiting, collapse, & death
what clinical signs are seen with cutaneous MCT in cats?
rare to see systemic signs - usually a lesion noticed by the owner that may be ulcerated
how are MCT diagnosed in cats?
FNA or biopsy
pre-medicate if aspirating the spleen - full of MAST CELLS!!!!!
how are MCT staged in cats?
CBC/chemistry/UA
FNA of regional lymph nodes
chest rads & abdominal ultrasound
what is the treatment used for cutaneous MCT in cats?
surgery - narrow margins are necessary
benign neglect - tumors often regress
what is the MST of visceral MCT in cats treated with splenectomy/surgery?
11-24 months
is chemotherapy used in cats with visceral MCT? what drugs?
it is but it is untested - used prednisolone, diphenhydramine, famotidine & watch it
vinblastine, lomustine, & chlorambucil
T/F: there is no worked out grading system for any type of MCT apart from dermal MCT
true - no grading established for tumors in the SQ
what organs are most commonly implicated in the visceral form of MCT?
liver & spleen
what is the only form of MCT that is the same in dogs & cats?
intestinal MCT
T/F: if CD117 is negative, it is not a mast cell tumor
true - all MCT will stain with CD117
what kind of receptors are tyrosine kinase? why are they a good target for drug therapy?
growth factor receptors
95% of protein interactions in the cell will not be affected by the inhibitor
instead of grading in cutaneous MCT in cats, what is provided instead?
whether the tumor is compact vs. diffuse
compact - lower grade, well circumscribed
diffuse - infiltrative, higher grade
why is a splenectomy done for a cat with visceral MCT?
every time the animal jumps/is picked up/squeezed - the mass degranulates further exacerbating clinical signs
