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11 Canine (and Feline) Mast Cell Tumors

Terms in this set (25)

Dogs who are predisposed to MCTs tend to be middle aged to older, with ___ breed being overrepresented
brachycephalic breeds

Boxers
Bulldogs
Boston Terriers
Shar-Pei
T/F Mast cell tumors are generally easy to recognize on physical exam because they consistently appear red, hairless, freely moveable, and ulcerated.
FALSE

MCTs do not have a consistent appearance; they are the 'great pretender' and can look like different
We don't know what causes canine MCTs to occur, but two gene mutations that appear to be associated with MCT formation are __ and __
p53 (tumor suppressor gene)

c-kit (aka Cd117)
All of the following staging steps can be taken to work up a MCT. Which are the most important?
-FNA of mass/cytology
-regional LN aspirates
-CBC, Chem
-TRX
-AUS
-Buffy coat
-Bone marrow aspirate
*-FNA of mass/cytology
-regional LN aspirates*
-CBC, Chem
-TRX
-AUS
-Buffy coat
-Bone marrow aspirate
T/F dogs with a MCT and regional LN involvement have a significantly shorter survival time.
TRUE
T/F You should perform an abdominal ultrasound when staging a MCT, but should not aspirate abnormal tissue (ex. in liver, spleen) because of the risk of hemorrhage and degranulation since MCTs secrete heparin, histamine, inflammatory cytokines, etc.
FALSE

Always aspirate anything abnormal in AUS

some clinicians even recommend aspirating the liver and spleen even if they appear normal
All of the following are prognostic factors for a mast cell tumor. The two (to three) most important prognostic factors are:

age
breed
histologic grade
location
mitotic index
stage
systemic signs.
*histologic grade

mitotic index*

(stage)
Match the histologic grade with their behavior:
Grade I, II, or III

low risk of mets
high risk of mets
aggressive local therapy
aggressive local invasion of tissue
chemotherapy indicated
shorter survival post-op
Grade I, II:
low risk of mets
aggressive local invasion of tissue
aggressive local therapy

Grade III:
high risk of mets
shorter survival post-op
local aggressive therapy (not enough alone)
chemotherapy indicated
What are the 3 criteria in the Patnaik grading scheme?

Note: Dogs with Grade 3 on the Patnaik scale are likely to die of MCT
1. Differentiation
2. Invasiveness
3. Mitotic Index per 10 hpf
Many MCTs fall into Patnaik Grade II. A helpful way to break down this category more is the mitotic index.

A mitotic index of =/<___ per 10 hpf is associated with a long survival time.

A mitotic index of >____ per 10 hpf is associated with tumor recurrence in ~5 mos.
=/<5 mitoses/10 hpf --> long survival

>5 mitoses/10 hpf --> recurrence in ~5 mos
Describe the staging system for Mast Cell Tumors.
Stage 0
Stage I
Stage II
Stage III
Stage IV
Stage 0 - incompletely excised
Stage I - single tumor confined to the dermis w/o regional LN involvement
Stage II - single tumor confined to dermis w/regional LN involvement
Stage III - multiple dermal tumors or large infiltrating tumor w/ or w/o regional LN involvement
Stage IV - distant mets present
T/F in a dog with several dermal MCTs, the number of tumors is not prognostic
TRUE
Give two treatment options for....
Curative intent

Palliative intent
Curative intent:
-wide or radical resection
-marginal resection + radiation
-chemotherapy

Palliative intent:
-cytoreductive sx
-palliative radiation
-systemic therapy
-chemotherapy
What margins are recommended for the best change of fully excising a MCT?

Remember - you don't know if it's Grade I, II, or III until you get your histopath back post-op
2-3 cm lateral margins
1 fascial plane deep

(~10% of Grade II tumors with 2cm excisions have dirty margins)
T/F shrinking a MCT with Triamcinolone or Prednisone is recommended before performing a curative intent wide resection
FALSE

not enough data to support tumor shrinkage pre-op. If you have curative intent, don't do it
the main tumor mass shrinks, but peripheral cells don't go away; you won't know where your margins should be
if you have palliative intent and are doing a marginal excision, go ahead
What is the post-op treatment for a MCT when the histopath report says:
Grade I or II
Low mitotic index
Clean margins
no further treatment
What is the post-op treatment for a MCT when the histopath report says:
Grade I or II
Low mitotic index
incomplete margins
additional surgery if larger margins are possible
+/- radiation

(local therapy)
What is the post-op treatment for a MCT when the histopath report says:
Grade II with high mitotic index
or
Grade III
Clean margins
adjuvant chemo
What is the post-op treatment for a MCT when the histopath report says:
Grade II with high mitotic index
or
Grade III
Incomplete margins
additional surgery
+/- radiation
adjuvant chemo
The main form of conventional chemo for MCTs is ___ and ___
vinblastine + prednisone
The main form of targeted chemo for MCTs is ____ or ____
Palladia (toceranib)
Kinavet (mastinib)

these target c-kit mutations
There are several palliative care drugs that are helpful when treating MCTs. The Top 2 are ___ and ___.
Other palliative therapies include:
-Omeprazole (PPI)
-Prednisone
-Chemo
-Radiation
Diphenhydramine (H1 antagonist)
Famotidine (H2 antagonist)
What are the two forms of feline MCTs? What is the most common signalment for each?
Mastocytic - middle age to older cats

Histiocytic - young Siamese cats; may spontaneously regress
T/F Feline cutaneous MCT have a poor prognosis
FALSE

Excellent px for feline cutaneous MCT - treatment of choice is surgery, you don't need aggressive margins.
Which visceral MCT has a poor prognosis, and which may have a good prognosis for cats?
GI MCT
Splenic MCT
GI MCT = poor

Splenic MCT = potentially good
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