Mast Cell Tumors Flashcards

1
Q

What is the most common skin tumor of dogs?

A

Mast cell tumors

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2
Q

What is a MCT nickname?

A

The Great Pretender

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3
Q

Why do MCTs often fluctuate in size

A

Degranulation

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4
Q

What do mast cell tumors contain?

A

Histamine, heparin, eosinophilic chemotactic factor, proteases

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5
Q

How do MCTs cause GI ulcers?

A

H2 receptor activation

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6
Q

Grading applies to which MCTs?

A

Dermal MCTs only

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7
Q

How do you grade an MCT?

A

Histopathology

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8
Q

What is the most common MCT grading scheme?

A

Patnaik

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9
Q

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

A

Grade 1 MCT

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10
Q

Low likelihood for recurrence and mets after removal

A

Grade 1 MCT

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11
Q

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

A

Grade 2 MCT

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12
Q

Low to moderate likelihood for recurrence and mets after removal

A

Grade 2 MCT

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13
Q

High likelihood for recurrence and mets after removal

A

Grade 3 MCT

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14
Q

Poorly differentiated, high mitotic index, invasive

A

Grade 3 MCT

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15
Q

What is considered a high mitotic index?

A

5+ mitoses/10hpf

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16
Q

Which grade of MCTs are most common (80%)

A

Grade 2

17
Q

What will a MCT look like on FNA cytology?

A

Individual round cells w/dark granules in cytoplasm and background

18
Q

What other WBC is commonly seen with MCTs?

A

Eosinophils

19
Q

How do you stage an MCT?

A

LN aspirate, abd ultrasound, thoracic rads

20
Q

Which LN should be aspirated to stage an MCT?

A

Dependent draining LN (not necessarily the closest one)

21
Q

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

A

2-3cm lateral margins + 1 fascial plane deep

22
Q

When is chemo indicated for MCTs?

A

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

23
Q

Which chemo agents are commonly used to treat MCTs?

A

Vinblastine, CCNU, Palladia, Pred

24
Q

What gene mutation is commonly found in aggressive MCTs?

A

c-kit

25
Q

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

A

Tyrosine kinase inhibitors (Palladia, Kinavet)

26
Q

What are supportive treatments used to minimize histamine degranulation?

A

H1 and H2 blockers

27
Q

Is having multiple dermal MCTs considered a negative prognostic indicator?

A

No - each tumor is treated individually

28
Q

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

A

Brachycephalics

29
Q

What do mast cell granules release?

A

Histamine, heparin, proteases, cytokines

30
Q

Can MCT grade be determined with cytology?

A

No

31
Q

What margins do you want when excising an MCT?

A

2-3cm lateral + 1 facial plane deep

32
Q

What chemotherapy is indicated for MCTs?

A

Vinblastine, CCNU or other alkylating agents

33
Q

How does prednisone support a MCT dog?

A

Cytotoxic to mast cells, reduces inflammation within the tumor

34
Q

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

A

Diphenhydramine

35
Q

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

A

Famotidine, ranitidine

36
Q

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

A

Palladia (Toceranib)

37
Q

What is the MoA of Palladia (Toceranib)?

A

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

38
Q

What are proliferation markers of MCTs used as prognostic indicators?

A

Ki-67, PCNA, AgNOR

39
Q

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

A

c-KIT mutation