Skin and Subcutaneous Tumours: Mast Cell Tumours Flashcards
How many of dog neoplasms are in the cutaneous?
25-30%
What % of cutaneous tumours are benign vs malignant
70 % vs 30%
Mean age of cutaneous tumour presentation?
8.3 years
Where are majority of cutaneous tumours on the dog?
Trunk (30%), head and neck (20%) and extremities (19%).
How many of cat neoplasms are cutaneous?
10%
What are the 4 common cutaneous neoplasia in cats?
Basal cell tumour
Mast cell tumour
Squamous cell carcinoma
Fibrosarcoma.
What tissue is involved in cutaneous tumours?
Skin or subcut
How are cutaneous tumours broadly classified? (5)
- Epithelial
- Adnexal
- Mesenchymal
- Round Cell
- Melanocytic
Epithelial cutaneous tumour examples (4)
- Basal cell tumours
- Papilloma
- SCC
- Nail bed tumours
Adnexal cutaneous tumour example (7)
- Sebaceous gland adenoma/adenocarcinoma
- Ceruminous gland adenoma
- Apocrine gland adenocarcinoma of anal sac
- Sweat gland tumours
- Trichoepithelioma
- Pilomatrixoma
- Meibomian gland adenoma
Mesenchymal cutaneous tumour example (1)
Soft tissue sarcoma
Round cell cutaneous tumour example (5)
- Mast cell tumour
- Histiocytoma
- Melanocytic nevi
- Plasmacytoma
- Lymphoma
Mealoncytic cutaneous tumour example (2)
- Benign cutaneous melanocytic nevi
- Malignant melanoma
What should happen to ALL skin/subcut masses prior to surgery?
FNA
When is pre treatment biopsy indicated? (4)
-If the tumour type will alter the type of treatment;
- If the histological grade of the tumour will alter the extent, surgical dose or treatment;
- If the tumour location limits the reconstructive options;
- If the tumour type and grade affect the owner’s willingness to pursue treatment based on prognosis.
How many of dog malignant cutaneous tumours are MCT?
20%
How common is cutaneous MCT tumour in cat?
2nd most common
Where can MCT arise from? (2)
- dermal
- sub cut
What do the characteristic cytoplasmic granules of MCT contain? (5)
- Histamine
- Heparine
-Proteases
-Chemotactic factors
Cytokines.
Dog age MCT?
Middle age - 5yr +
Breeds more commonly seeing MCT? (6)
Boxers, Boston Terriers, Golden Retrievers, Labrador Retrievers, Beagles and Schnauzers
Which breed is more likely to have multiple MCT at time of diagnosis? What is the behaviour of these?
Pugs
- more benign
How many MCT:
A) Occur on trunk?
B) on limbs?
A) 50-60%
B) 25%
The majority of MCTs will be diagnosed on cytology following FNA. The typical path of metastatic spread is initially to the A) and then to B) liver or bone marrow. Cutaneous MCTs rarely metastasise to the C)
A) Regional LN
B) Spleen
C) lungs
What does staging of a MCT involve? (3)
Local tumour FNA
Regional lymph node aspirates
Abdominal ultrasound
Should we aspirate spleen/liver when staging MCT?
not routinely recommended
What is the general behaviour of a eyelid MCT?
Relatively benign
Where do MCT have more aggressive biologic behaviour, with increased risk of locoregional LN metastasis? (3)
Muzzle
Perioral mucocutaneous junction, Oral mucosa
Do we apply cutaneous MCT grading to subcut MCT grading?
NO.
Dog subcut MCT:
A) how many had local recurrence?
B) How many had mets?
A) 8%
B) 4%
What is the most important single prognositc factor for MCT?
Histopath grading
MCT - where should pre op biopsies be taken if needed?
A site that their excision might be readily included in the subsequent treatment protocols, without the need to enlarge the surgical site or radiation field.
What is the most widely used grading system for cutaneous tumours?
The Patnaik (1984) system
What is the problem with The Patnaik (1984) system?
SUBJECTIVE - less than 64% agreement between pathologists for grade one and two MCTs and 75% agreement for grade three.
Patnaik grade one (low):
A) Grade?
B) Microscopic feature
A) Well differentiated
B) Well differentiated mast cells with clearly defined cytoplasmic borders with regular spherical or ovoid nuclei
Granules are large, deep staining and plentiful
Cells confined to dermis and interfollicular spaces
Patnaik grade two (intermediate):
A) Grade?
B) Microscopic feature
A) Intermediately differentiated
B) Cells closely packed with indistinct cytoplasmic boundaries
Nuclear/cytoplasmic ratio lower than anaplastic
Frequent mitotic figures
More granules than anaplastic
Neoplastic cells infiltrate or replace the lower dermal and subcutaneous tissues
Patnaik grade three (high)):
A) Grade?
B) Microscopic feature
A) Anaplastic/Undifferentiated
B) Highly cellular, undifferentiated cytoplasmic boundaries
Irregular size and shape of nuclei
Frequent mitotic figures
Low number of cytoplasmic granules
Neoplastic tissue replaces the subcutaneous and deep tissues
What two-tier grading system is used to reduce subjective nature of grading?
Kiupel
Kiupel system - high grade has one of the following criteria:
- MI of ≥7
-Three or more multinucleated cells or cells with bizarre nuclei in 10 high-power fields, or karyomegaly. - Areas of highest mitoses or anisokaryosis were evaluated.
How many dogs with MCT have a mutation of c-KIT gene? What is this associated with? (3)
15-40%
Increased mets, local recurrence, high histo grade
What should be performed prior to incision of MCT?
FNA of LN
When is the only times thorax radiography is indicated for MCT? (2)
- sternal MCT - looking at sternal LN
- rule out other poss causes of mets
What preparation is used to look for circulating mast cells (but is insens and non specific)
Buffy coat
Describe clinical stage 0 MCT
Single tumour
Incompletely excised
Remain in dermis
Describe clinical stage I MCT
Single tumour
Confined to dermis
Without local lymph node involvement
Describe clinical stage II MCT
Single tumour
Confined to dermis
With local lymph node involvement
Describe clinical stage III MCT
Multiple dermal tumours or large infiltrating tumour
With or without regional lymph node involvement
Describe clinical stage IV MCT
Any tumour with distant metastases
Including to blood and bone marrow
Which of these statements are true?
A) Radiographs are indicated to evaluate the pulmonary spread of MCTs.
B) Any tumour with distant metastases is classified as grade IV (clinical stage).
C) Cytologic assessment of the locoregional LN is important, even if the node is not enlarged.
B) Any tumour with distant metastases is classified as grade IV (clinical stage).
C) Cytologic assessment of the locoregional LN is important, even if the node is not enlarged.
What is advised for peri-operative treatment for tumours that will be surgically manipulated, or those that show evidence of degranulation or melena and haemoptysis associated with gastrointestinal ulcerations?
H1 blocker (e.g., chlorphenamine) and H2 blockers (e.g., ranitidine)
Neoadjuvant prednisolone has been shown to reduce MCT by…
up to 80% (in 70% of patients)
Recommended lateral and deep margins for MCT?
Lateral - 3cm
Deep - One tissue plane
When are lateral margins of 2cm and deep of 1 fascial plane ok for a mct? (2)
- intermediate grade
- low grade
If less than 4cm
What is the local recurrence in intermediate MCT (after complete Sx exicsion)
23%
Where incomplete margins have been demonstrated following excision of low or intermediate-grade MCTs, local recurrence is not guaranteed. Decision making in such a situation is not straightforward and current recommendations for such cases include: (3)
Monitoring the site
Follow-up radiation therapy
En bloc excision of the scar with appropriate gross margins (2 cm laterally and one fascial plane).
What should follow complete removal of a high grade MCT?
Chemo
When should you consider amputation?
Grade III distal MCT
What is the primary choice for residual postsurgical microscopic disease.
Radiotherapy
In patients with MCTS in the distal limbs, where achieving clean deep margins is not possible because the MCT is wrapping around tendon, what is the surgical aim?
(there is little to gain in attempting to achieve clean lateral margins and) the surgeon should aim for the removal of all gross disease and achieve simple primary closure.
The surgeon should collaborate closely with the radiotherapist and take numerous pre, intra, and postoperative photographs to ensure there is not a geographical miss when radiation therapy is performed.
What control rate does radiation therapy offer after incomplete excision of low and intermediate-grade MCTs?
3 year (in 90%)
What sign is both an acute and late effect of radiation?
Alopecia
Acute effects radiation? (2)
Dry desquamation
Alopecia
Later effects radiation? (2)
Alopecia
Leukotrichia
When is chemotherapy useful in MCT management situations? (3)
Neo-adjunctive to reduce tumour burden prior to complete surgical excision or radiation (such as prednisolone).
Where systemic therapy is required, such as in high-grade tumours or where metastasis has been documented or is likely.
Where microscopic disease is present and further surgery or radiation is not possible.
MCT:
A) First line chemo?(2)
B) Second line chemo? (1)
A) Vinblastine and prednisolone
B) Lomustine
What is a common chemo protocol to treat dogs with aggressive MCT without evidence of gross disease?
vinblastine/prednisolone consists of an eight-dose protocol
- If measurable disease is present, then the treatment is based on effect – with continued weekly doses until maximum response, then every 2 weeks, decreasing administration to as infrequent as possible to still maintain tumour control.
Adverse effects of vinblastine? (3)
- Perivascular irritant
- Myelosupression
- GI toxicity
Adverse effects of lomustine (2)
- Myelosuppression
- Hepatic toxicity
How do tryosine kinase inhibitors work?
competitively block extracellular domains of receptor tyrosine kinases, which then prevents the activation and phosphorylation of the intracellular domains responsible for cell proliferation, differentiation and survival, and angiogenesis and metastasis.
