Mast Cell Tumors

Question 1

What is the most common skin tumor of dogs?

Answer 1

Mast cell tumors

Question 2

What is a MCT nickname?

Answer 2

The Great Pretender

Question 3

Why do MCTs often fluctuate in size

Answer 3

Degranulation

Question 4

What do mast cell tumors contain?

Answer 4

Histamine, heparin, eosinophilic chemotactic factor, proteases

Question 5

How do MCTs cause GI ulcers?

Answer 5

H2 receptor activation

Question 6

Grading applies to which MCTs?

Answer 6

Dermal MCTs only

Question 7

How do you grade an MCT?

Answer 7

Histopathology

Question 8

What is the most common MCT grading scheme?

Answer 8

Patnaik

Question 9

Well differentiated, low mitotic index, small and superficial in dermis

Answer 9

Grade 1 MCT

Question 10

Low likelihood for recurrence and mets after removal

Answer 10

Grade 1 MCT

Question 11

Moderately differentiated, low/mod mitotic index, mild/mod invasive

Answer 11

Grade 2 MCT

Question 12

Low to moderate likelihood for recurrence and mets after removal

Answer 12

Grade 2 MCT

Question 13

High likelihood for recurrence and mets after removal

Answer 13

Grade 3 MCT

Question 14

Poorly differentiated, high mitotic index, invasive

Answer 14

Grade 3 MCT

Question 15

What is considered a high mitotic index?

Answer 15

5+ mitoses/10hpf

Question 16

Which grade of MCTs are most common (80%)

Answer 16

Grade 2

Question 17

What will a MCT look like on FNA cytology?

Answer 17

Individual round cells w/dark granules in cytoplasm and background

Question 18

What other WBC is commonly seen with MCTs?

Answer 18

Eosinophils

Question 19

How do you stage an MCT?

Answer 19

LN aspirate, abd ultrasound, thoracic rads

Question 20

Which LN should be aspirated to stage an MCT?

Answer 20

Dependent draining LN (not necessarily the closest one)

Question 21

What margins do you want to get for MCTs w/o mets?

Answer 21

2-3cm lateral margins + 1 fascial plane deep

Question 22

When is chemo indicated for MCTs?

Answer 22

Grade 3/high grade 2 tumors, if mets are present, unresectable tumors

Question 23

Which chemo agents are commonly used to treat MCTs?

Answer 23

Vinblastine, CCNU, Palladia, Pred

Question 24

What gene mutation is commonly found in aggressive MCTs?

Answer 24

c-kit

Question 25

Which chemo drugs target the mutated c-kit gene found in MCTs?

Answer 25

Tyrosine kinase inhibitors (Palladia, Kinavet)

Question 26

What are supportive treatments used to minimize histamine degranulation?

Answer 26

H1 and H2 blockers

Question 27

Is having multiple dermal MCTs considered a negative prognostic indicator?

Answer 27

No - each tumor is treated individually

Question 28

Which dog breeds frequently develop multiple MCTs over their lifetime but are usually assoc. w/lower grade tumors?

Answer 28

Brachycephalics

Question 29

What do mast cell granules release?

Answer 29

Histamine, heparin, proteases, cytokines

Question 30

Can MCT grade be determined with cytology?

Answer 30

No

Question 31

What margins do you want when excising an MCT?

Answer 31

2-3cm lateral + 1 facial plane deep

Question 32

What chemotherapy is indicated for MCTs?

Answer 32

Vinblastine, CCNU or other alkylating agents

Question 33

How does prednisone support a MCT dog?

Answer 33

Cytotoxic to mast cells, reduces inflammation within the tumor

Question 34

What H1 blocker (histamine) can you give to relieve consequences of mast cell degranulation?

Answer 34

Diphenhydramine

Question 35

What H2 blocker (histamine) can you give to relieve consequences of mast cell degranulation?

Answer 35

Famotidine, ranitidine

Question 36

What is the first FDA-approved drug for canine cancer in the US?

Answer 36

Palladia (Toceranib)

Question 37

What is the MoA of Palladia (Toceranib)?

Answer 37

Inhibits aberrant cell signaling pathways found in MCTs (tyrosine kinase inhibitor)

Question 38

What are proliferation markers of MCTs used as prognostic indicators?

Answer 38

Ki-67, PCNA, AgNOR

Question 39

Dogs with which gene mutation assoc. w/MCTs have a worse prognosis?

Answer 39

c-KIT mutation