Mast cell tumours

Question 1

Outline the make up of mast cell tumours

Answer 1

 Start as CD34+ progenitor’s in bone marrow
 Mature in peripheral tissue
 Barrier’s – GIT, skin, lungs
 Granules contain
▪ Histamine and heparin amongst others
▪ Released due to trauma, heat, IgE binding

MCT granules can be stained after released into periphery, not before
Can use Touridine blue stain for histo.

Question 2

Where do you get MCTs?

Answer 2

 Most commonly cutaneous
 Occasionally mucocutaneous
 Rarely visceral,GI or bone marrow

Question 3

What are the common breeds for MCT

Answer 3

 Brachycephalics,GRT and Labs predisposed.
▪ Boxers and Pugs mostly low grade
▪ Sharpei’s more aggressive disease

Question 4

What is darier’s sign?

Answer 4

A wheal around the tumour

Question 5

How common is it to get more than one tumour?

Answer 5

10-20% dogs will have more than 1 at dx

40% will get more than one in life

Question 6

Compare FNAs and biopsies

Answer 6

 FNA
 Round cell (fried egg) with variable numbers of
granules
 Some correlation with grade but biopsy better
 Biopsy – incisional
 Grading information
 MI
 Can measure proliferation indices

Question 7

What are the main grading systems?

Answer 7

 Patnaik currently currently most used
 Good differentiation between high and low
 Grade 2 problematic

 Kiupel
 Two grade system
 Some improvement in performance

Question 8

What is the use of proliferation indices?

Answer 8

 MI
▪ >5 is bad
▪ No additional cost
▪ Good link with prognosis prognosis
 Ki67
▪ Independent risk factor for recurrence, metastasis and death

Question 9

How does grade reflect metastatic rate?

Answer 9

Metastatic rates
 Grade 1 – 10 % or less
 Grade 2 – 22% or less
 Grade 3 ~ 80%
 Therefore I discuss staging for all MCTs and recommend staging for:
 all G2 and G3 tumours
 all tumours with aggressive appearance or behaviour
 all recurrences – upstaging?

Assume all grade 3s have spread

Question 10

What staging should be done?

Answer 10

 Aspiration of local lymph nodes
 Thoracic radiographs
 Tumours located in areas that drain to thoracic lymph
nodes
 Abdominal ultrasound
 Aspiration of spleen and liver
 There can be metastatic disease in the liver without
ultrasonographic structural abnormalities

Question 11

What factors affect prognosis?

Answer 11

 Possibly breed  Appearance  Location
 Controversial but possibly scrotal or inguinal worse
 Recurrence after surgery
 LN and distant metastasis
 Grade  High proliferation markers  Kit mutation
 Poor response to medical therapy

Question 12

What is the order of preference for local treatment of MCTs?

Answer 12

 Surgery
 Neoadjuvant medical therapy then surgery
▪ Surgery and RT
▪ rTKI
 Other medical therapy
rTKI inhibitors are not a substitute for surgical excision

Question 13

Outline the use of Sx in MCT tx

Answer 13

 Treatment of choice for localised non‐metastasised
MCTs
 Loco‐regional control improves outcome even in higher grade disease
 Combination of surgery and radiation therapy effective forG1 and 2 tumours with nodal metastasis
 Manipulation carries a risk of degranulation
 Gentle handling
 Consider pre and perioperative anti‐histamines

Question 14

How radical does surgery need to be?

Answer 14

 Grade is known
 ‘Concerning’ grade 2 and grade 3
▪ 3 cm laterally and 1 fascial plane/muscle layer deep to the deepest tumour tissue
 Grade 2 or 1
▪ 2 cm laterally and at least 1 fascial plane
 Grade unknown
 3 cm laterally and 1 fascial plane/ muscle layer deep to the deepest tumour tissue

Question 15

What are the options if you are not confident in getting a good margin?

Answer 15

 Refer to a soft tissue surgeon
 Surgery alone
▪ Surgery followed by radiation therapy
 Neoadjuvant treatment
 Prednisolone
 VBL + Prednisolone
 Tyrosine kinase inhibitor (licenced)
▪ Masitinib /Toceranib

Question 16

Outline the use of neoadjuvant therapy

Answer 16

 Aim – to shrink a non‐resectable tumour
sufficiently to allow resection
 Prednisolone
▪ 2.2 mg/kg for 10 days OOR of 70%
▪ mean 50% reduction in size
 Vinblastine and prednisolone
▪ no more than 2 cycles
▪ Also thought to reduce size indicated in high risk
tumours as adjuvant therapy

Question 17

Outline the use of tyrosine kinase inhibitors in gross disease

Answer 17

 Mastinib
 50% have ~ 50% reduction in tumour size within 6
months
 Toceranib
 ~ 40% response rate in ‘non‐resectable disease’
BUT HOW LONGUNTIL MAXIMUM EFFECT?
BUTWHEN DOYOU STOP?

Question 18

What are the indications for adjunctive therapy?

Answer 18

 Confirmed metastasis
 High k ris tumours
 Grade 3
 Other grade with high MI
▪ Other grade with high KI 67

Question 19

Outline the use of prednisolone and vinblastine

Answer 19

 8 cycle protocol
 Staging before first and after last treatment.
 Haematology before each treatment
 Adjuvant treatment
 All tumours MST > 570 days
 Grade III – MST 330 days

Question 20

How often should follow up/ staging be performed?

Answer 20

 Regular follow up is indicated for all tumours
 Re‐staging based upon risk
 At the end of treatment
 One month after the end of treatment
 Then every 3 months for at least a year
 Then every 6 months to a year
 If the patient is unwell

Question 21

Outline oral/ perioral MCTs

Answer 21

 Comparatively rare presentation
 Cutaneous grading scheme does not apply
 MST prolonged prolonged – 52 mths
 But shorter with nodal metastasis – 14 mths

Question 22

Outline subcutaneous MCTs

Answer 22

 Cutaneous grading systems unproven
 Combination of following predictive of outcome
▪ MI
▪ Ki‐67
▪ KIT cellular localisation

Question 23

Outline multiple cutaneous MCTs

Answer 23

 Not clear whether these are metastatic or not
 Prognosis for multiple MCTs treated with surgery
is not necessarily worse than single MCTs
 However
 High rate of de novo appearance of new tumours
▪ Often low grade
 Treatment
 Repeat surgeries
 Short course of chemotherapy

Question 24

Outline BM/ visceral/ GI MCTs

Answer 24

 Rare in dogs  GI disease poorly reported
 Prognosis seems to be variable
 Visceral disease
 Reported MST of 90 days
 Newer / more aggressive adjuvant therapy may improve
this
 Bone Marrow
 Poor survival ~ 45 days
 Poor response to conventionaltreatments