Ch 82 MCT

Question 1

MCT

most common tumour

Answer 1

• precursors originate from CD34+ progenitor cells in bone marrow, migrate to peripheral tissues and differentiate into mature mast cells.
• involved in inflammation and immunoglobulin E (IgE)-mediated immunity.
• granules: histamine, heparin, proteases, chemotactic factors, cytokines, and metabolites of arachidonic acid.
• granules stain with cationic dyes.
• visceral form (disseminated or systemic mastocytosis)
• trunk (42% to 65%), followed by the limbs (22% to 43%)
• Extracutaneous sites: conjunctiva, oral cavity, salivary gland, larynx, nasopharynx, trachea, gastrointestinal tract, ureter, and spine

Question 2

What breeds are predisposed to MCT?

multiple cutaneous mast cell tumors?

Answer 2

Boxers
Boston Terriers
Pugs
Bull Terriers
Bullmastiffs
Cocker Sp

multiple: Boxers, Pugs, Staffy, Golden Retrievers, and Weimaraners

Question 3

Etiology

Answer 3

• largely unknown and is probably multifactorial
• genetic factor is likely, considering several breed predisposition
• Stem cell factor (stimulator of differentiation) binds to the growth factor receptor KIT (CD117)
• KIT = tyrosine kinase receptor involved with biologic activities (proliferation, migration, and maturation)
• KIT is encoded by the protooncogene c-kit
• 15% to 50% of mast cell tumors are affected by c-kit mutations
• significantly associated with tumor grade, recurrence and death

Question 4

WHat mutation is seen in up to 50% of canine MCT?

Answer 4

C-kit

significantly associated with tumor grade, recurrence and death

Question 5

presentation, degranulation, systemic dz

Answer 5

• Up to 25% of dogs are presented with multiple tumors
• growth rate and clinical appearance associated with histologic grade and prognosis
• dermal or subcutaneous

degranulation
- size fluctuation, edema, erythema, and inflammation (Darier sign, associated with a worse prognosis)
- provoked by manipulation
- paraneoplastic syndromes
- histamine > gastrointestinal ulceration (gastric acid production [H2] receptors, vascular damage, and hypermotility) general GIT signs
- Postoperative delayed wound healing: several studies not found a difference
- heparin > increased bleeding

disseminated (systemic) mastocytosis
- systemic spread of primary cutaneous mast cell neoplasia
- lymphadenopathy, splenomegaly, and hepatomegaly
- Involvement of bone marrow and peripheral blood
- Primary visceral and bone marrow involvement poor prognosis

Question 6

mets

Answer 6

• regional draining lymph nodes and later in the spleen and liver.
• lungs is highly uncommon
• Multiple cutaneous: may be mets or de novo (px still determined by grade]

Question 7

Grade

Answer 7

Patnaik
- well-differentiated (grade 1),
- intermediate (grade 2),
- undifferentiated (grade 3).
- metastatic rate (to lymph nodes or distant sites)
- low-grade (grade 1) <10%
- intermediate (grade 2) 2-20%
- high-grade (grade 3) 12-96%

problems with Patnaik
- tumor invasion = dermis and expanding into the subcutis.
- Strict application of this system does not consider well-differentiated tumors originating from the subcutis (which have a better prognosis)
- Large variation in outcome and grading amongst pathologists > inconsistency between grade 1 versus grade 2 among pathologists together with the relatively good outcomes of many grade 2 tumors suggests those grade 2 tumors are “low grade’

Kiupel
- low grade (85% of Patnaik grade 2)
- high grade
- high interobserver consistency
- significant prognostic relevance: MST 690-1452 days versus 110-208 days for low- versus high-grade tumors

Question 8

significant prognostic factors:

Answer 8

• invasive growth pattern
• Mitotic index

Question 9

Dx and staging

Answer 9

• diagnosed > 96% through cytology
• Romanowsky-type stains (diff-quik)
• Some undifferentiated mast cell tumors have no clearly staining granules
• grade of malignancy, and thus prognosis, only by histologic grade
• Lymph node status is a prognostic factor for survival, independent of tumor grade
• 15% Kiupel low-grade
• 30% Kiupel high-grade

(WHO) clinical staging scheme
- Controversy about its validity, concerning multiple cutaneous tumors and the term dermis
- Multiple cutaenous automatically categorized as stage 3 and thus poor px (not supprted by literature)
- grade 2 and 3 tumors are by definition not confined to the dermis and could therefore be categorized as stage 3

staging
- FNA/biopsied l.n. even if they are normal in size
- Determination of lymph node metastasis can be tricky because mast cells are present in normal lymph nodes (look for sheets, atypia)
- extirpation recommended for definitive dx and therapeutic
- abdominal ultrasonography with emphasis on evaluation of liver and spleen +/- FNA regardless of appearance

Question 10

survival

Answer 10

Grade 1/2 low-grade: 700-<1300d

Grade 3/high grade 100-380d

1yr survival 1 100% 2 90% 3 50%

Question 11

recurrence rates

Answer 11

• known or unknown margin status were 1% for grade 1, 5% to 11% for grade 2, and 19% for grade 3 mast cell tumors
• reported recurrence (or occurrence) of mast cell tumors at other sites in the skin after resection of a primary mast cell tumor 22% to 38% overall (all grades)

Question 12

Tx considerations

Answer 12

• depeneds on clinical stage, histologic grade, anatomic location
• most important prognostic factor is histologic grade
• Patnaik 1-2 or Kiupel low-grade best treated using wide resection surgery or marginal surgery combined with radiation therapy
• High-grade, high-risk (stage 2), and irresectable tumors treated best using a multimodal approach (wide exicsion or margina with radiation plus chemo)
• improved survival compared to only primary tumor excision with lymphadenectomy of metastatic nodes

Question 13

surgical margins

Answer 13

• tend to invade and spread into surrounding tissues
• Surgical excision is the therapy of choice for all grades
• Historically, 3 cm of macroscopically normal tissue with the deep margin (fascia > dense collagen/vascular poor tend to behave as biologic barriers)
• lateral margin reocmmendations have been challeneged
  1. grade 1 with 1 cm margin (100%) and grade 2 with 2 cm (85-100%) excised
  2. A modified proportional margin approach with lateral margins equal to the size of the tumor diameter up to maximum 2cm > 95% excised regardless of grade

Question 14

Prognostic Factors

Answer 14

Clinical Presentation (-ve)
- darier sign
- Systemic signs associated with viceral
- large tumors >3 cm (vs slow growing, present for >6mths +ve)

tumor location

stains/histo
- unpredictable nature based on histologic grade alone, grade 2 mast cell tumors may be further classified
- nuclear proliferation marker Ki-67 was significantly related to decreased survival time,
- Mitotic index is significantly related to recurrence, metastasis, and survival time

Clinical Stage
- stage 0 or 1 has a better prognosis compared with higher stages (stage 1 usually several years)
- lymph node metastasis at the time of diagnosis significantly shortens survival
- stage 2 treated may have comparable MST to stage 0 (multimidal approach)

margins
- grade 3 carry a poor prognosis (survival < 3 months) after incomplete resection).
- MST of complete not different compared with incomplete resection of grade 2
- only 5% to 23% local recurrence has been reported for grade 2 dirty margin
- 4% local recurrence after complete excision of Kiupel low-grade with no difference bwteen wide and narrow margins
- Kiupel high-grade tumors have a higher chance of local recurrence.
- overall data suggets incomplete margins = higher rate of local recurrence + local recurrence is significantly related to decreased survival time
- low recurrence incompletely excised grade 1 and 2 > cells less atypical than those of high-grade tumors, making it more difficult to distinguish between normal and neoplastic mast cells, tumor chemotatctic agens recruiting normal mast cells

Question 15

What MCT locations may be associated with a poorer prognosis?

Answer 15

• Preputial
• Scrotal
• Subungal
• Oral and other mms
• Perineal and inguinal sites
• Perioral/muzzle
• Visceral or bone marrow involvement

Question 16

What special stains can be used for MCT which may help to prognosticate?

Answer 16

IHC of Ki-67 (nuclear proliferation marker)
PCNA
AgNOR using silver-based stains

Question 17

Radiation Therapy

Answer 17

• most effective therapies for incompletely excised low- to intermediate-grade tumors without metastasis are scar revision or radiation therapy of the wound bed
• median survival time was significantly increased after wide reexcision (2930 days) or radiation therapy (2194 days) compared to no additional local therapy (710 days)
• distal extremity grade 1 and 2 best treated by a combination of marginal resection and adjuvant radiation therapy (alternative to radiacal amputation)
• lymph node irradiation improved outcome for grade 3

Question 18

chemotherapy

Answer 18

• most studies evaluating chemotherapy lack a control group, lack standardization, include patients with incompletely excised grade 2 mast cell tumors, and include patients that also received other treatments (e.g., radiation).
• high-risk grade 2 mast cell tumors (high mitotic index, lymph vessel infiltration, incomplete margins) for metastasis of grade 3 may warrent chemo
• Oral prednisone > reduce the size of tumors in 20% to 75% of the cases
• generallt poor resposnse rates for singe agent (<27%)
• response rates 47% to 65% for vinblastine/prednisone, vinblastine/cyclophosphamide/prednisone > MST macroscopic disease may be shorter than for microscopic disease
• prolong disease-free interval and survival, it did not prevent development of mast cell tumors at distant sites in the skin in 25% of the cases.
• Chemotherapy-induced toxicity was moderate to severe in 22% to 41% of patients treated with CCNU

Question 19

electrochemotherapy

Answer 19

histologic grades 1 to 3 were treated with intratumoral application of bleomycin followed by local application of biphasic electrical pulses. The overall response rate was 85%, and the mean estimated time to recurrence was 53 ± 7 month

Question 20

Tyrosine Kinase Inhibitors

Answer 20

• mutation of the receptor tyrosine kinase KIT, found in 15% to 50%
• methods of testing for such mutations, which in general are relatively insensitive and probably cause an underestimation (so dogs without mutation may repsond to tx)
• masitinib and toceranib
• increased progression-free interval and MST compared to placebo for grade II and III tumors
• Response rate was higher (69%) for tumors with c-kit mutations
• Adverse events (mainly mild to moderate gastrointestinal signs)

Question 21

outcome

Answer 21

• definitive evidence-based treatment protocol is hard to establish because of a lack of controlled studies, especially for higher grade mast cell tumors.
• regardless of tx/grade, MCT areunpredictable, local recurrence is common as wellas 25% chance of distant “recurrence” or de novo
• Surgical excision is the therapy of choice for grade 1 and 2 mast cell tumors, in which a 2-cm margin and at least one fascial plane sufficient for local tumor control in most cases
• surgery, radiation, or both combined with chemotherapeutics to control metastatic rate is indicated for poorly differentiated or incompletely resected grade 3 mast cell tumors and high-risk grade 2 mast cell tumor

Question 22

Feline Mast Cell Tumors

Answer 22

• Siamese, Burmese, Russian Blue, and Ragdoll may be more susceptible to develop mast cell tumors
• 2.4 to 2.9 years for the histiocytic form
• Histiocytic> regress spontaneously in 4 to 24 months
• well differentiated (compact) >benign
• poorly differentiated (diffuse or pleomorphic) >malignant
• primary visceral mast cell tumors, either splenic or intestinal, occur more frequently in cats and NOT associated with cutaneous

presentation
- dermal or subcutaneous nodules, Multiple reported
- head and neck are the most common sites

Question 23

mets and staging

feline

Answer 23

• Systemic metastasis rates for cutaneous tumors 0% to 22%
• metastasis are much more common with visceral > 90% to liver
• Peritoneal and pleural effusions in 1/3
• Mastocytemia 30%, 100% in viceral
• Intestinal tumors, usually located in the small intestine as solitary or multiple lesions, often metastasize and have a poor prognosis

dx + staging
- FNA masses, an enlarged spleen, and peritoneal or pleural effusion
- mastocytemia diagnosed in a buffy coat smear
- Diagnostic imaging (radiography, ultrasonography,

Question 24

treatment

feline

Answer 24

• Most cutaneous mast cell tumors in cats can be considered behaviorally benign and can be adequately managed by local therapy > surgery
• Median survival times were not reached in most studies.
• poorly differentiated tumors, especially those showing a high mitotic rate, are probably better treated with a more aggressive approach
• strontium-90 plesiotherapy (<2.5cm) MST 1000d

Question 25

prognosis

feline

Answer 25

• histologic grading of feline mast cell tumors is not prognostic
• Local recurrence after surgical resection has been reported to be 0% to 33% (margin not matter)
• Mitotic index seems to be the most effective prognostic factor
• mutiple tumors possibly associtaed with reduce MST
• splenic mast cell tumor, long-term survival of 12 to 19 months reported after splenectomy
• intestinal MST generally poor progosis (<2mths), possibly prologed with multimodal tx (sx + chemo_)

Question 26

Three major recognized canine histiocytic disorders

Answer 26

• cutaneous histiocytoma (benign skin tumor of Langerhans cells, young, spotaeous regress 1-2mths or sx curative)
• reactive histiocytosis (cutaneous > benign condition in which aggregates of histiocytes form infiltrative nodules, plaques) and (systemic > nonneoplastic disease of proliferative histiocytes in Bernese Mountain Dogs, Rottweilers)
• histiocytic sarcoma (Bernese Mountain Dogs; Flat-Coated, Golden, and Labrador Retrievers; and Rottweilers (disseminated form has a poor prognosis) whereas (localized cutaneous commonly more favorable with surgical excision)

Question 27

Cutaneous Lymphoma

Answer 27

• epitheliotropic T-cell lymphoma (also termed mycosis fungoides) or nonepitheliotropic lymphoma,
• localized cutaneous lesions to multifocal or generalized (nodules, plaques, ulcers, and erythematous or exfoliative dermatitis)
• generally treated systemically, except in rare cases of a solitary cutaneous mass

Question 28

weishaar lymph node staging

Question 29

Saunders 2021 – modified proportional margin approach for cutaneous MCT

Answer 29

excision of cutaneous MCT with lateral margins equal to tumour diameter up to max 2cm
→ 95% complete excision – no association with tumour grade or size
- recurrence rate 3/100 (3%), de novo development 5/65 (7.7%)
- recurrence rate associated with high-grade MCT regardless of margin status
- post-op metastasis 3/65 (4.6%)

Question 30

Long-term outcomes of dogs undergoing surgical resection
of mast cell tumors and soft tissue sarcomas: A prospective
2-year-long study
Milan Milovancev 2020

Answer 30

20mm margins for MCT + 1 fascial plane
tumor-free margins measured <1 mm in 21 of 52 (40%) MCT
Two of 50 (4%) low-grade MCT were diagnosed, with local recurrence
Two of 36 (6%) dogs
with low-grade MCT developed visceral metastasis
Local recurrence rates among predominantly low- to intermediategrade
MCT and STS were low, despite a high prevalence of histologic tumor-free
margins <1 mm.

Question 31

Mast cell tumours in dogs less than 12 months of age: a multi-institutional retrospective study
K. Rigas 2020

Answer 31

After varying treatment protocols, all patients were alive and disease free at a median of 1115 days after diagnosis.
Four cutaneous mast cell tumours were described as high-grade (Patnaik or Kiupel) and nine were Patnaik grade II

The prognosis of mast cell tumours in dogs less than a year old appears better than the adult counterparts

Question 32

Variability in tumor margin reporting for soft tissue
sarcoma and cutaneous mast cell tumors in dogs:
A systematic review
Brittany E. Abrams

Answer 32

Most
(56.6%) studies reported the status of histologic margins dichotomously as
“complete” or “incomplete.”
only 7.5% of articles used quantitative methods.

A universal system may support
more consistent reporting of neoplastic biopsy specimens and allow for more
meaningful comparisons across research studies.

Question 33

Prognostic Indicators and Clinical Outcome in
Dogs with Subcutaneous Mast Cell Tumors
Treated with Surgery Alone: 43 Cases
Gill

JAHAA

Answer 33

Median PFS was
1474 days. Median DFI was not reached at .1968 days. Overall median survival time was not reached at 1968 days.
mitotic index were negatively prognostic for PFS

cutnaeous: Kiupel proposing a two-tier grading
scheme found high-grade tumors to have at least one of the following:
seven or greater mitotic figures in 10 high-power fields
(hpfs); at least three multinucleated (three or more nuclei) cells in
10 hpf; at least three bizarre nuclei in 10 hpf; and karyomegaly

unknown
if the Patnaik or two-tier grading scheme can be appropriately ap
plied to this subset of tumors

Question 34

Retrospective analysis of outcome and prognostic factors of subcutaneous mast cell tumours in dogs undergoing surgery with or without adjuvant treatment
E Treggiari 2023

VCO

Answer 34

retrospectively review
- Recurrence rate was 15%
- 63% of evaluated lymph nodes were consistent with early/overt metastasis.
- MST 83-1357 days
- median time to progression 14-1357 days) were not reached.
- Factors predictive of shorter survival: older age, clinical signs, mitotic count >4, multinucleation

our study suggests that dogs with SC MCTs, in the absence of negative prognostic factors, may have a prolonged survival when treated with surgery alone.
Further studies are needed to clarify the role of adjuvant treatment for biologically aggressive SC MCTs in dogs

Question 35

Evaluation of scar revision after inadequate primary
excision of cutaneous mast cell tumors in 85 dogs
(2000–2013)
Karbe 2021

Answer 35

Retrospective study
Residual MCT was found (27%) resected scars.
Seven (8%) scars with residual MCT had incomplete (<1mm) or narrow margins (<3mm).
Local recurrence (4%)
(14.5%) regional or systemic metastasis
Margin status and presence of MCT in the resected scar were not associated with local recurrence or disease progression
recurrence and mets siginficantly more likely with grade IIII

recurrence was uncommon after surgical revision

Question 36

Marginal excision of cutaneous mast cell tumors in dogs was not associated with a higher rate of complications or prolonged wound healing than marginal excision
of soft tissue sarcomas
Elspeth Cockburn 2022

Question 37

Utility of Spleen and Liver Cytology in Staging of
Canine Mast Cell Tumors
Megan Brown

JAAHA

Answer 37

Overall, 22 (10.7%) patients had metastasis, with 21 (10.2%) and 13
(6.3%) having spleen and liver metastasis, respectively, and 12 (5.9%) having both.
negative spleen cytology had a higher predictive value (0.99) than a positive cytology
spleen cytology is predictive of liver cytology in staging of canine MCTs, and increasing tumor size and presence of
local or systemic signs are associated with an increased risk of visceral metastasis
suggesting that
adequate staging may be achieved with spleen cytology alone

Question 39

review 2022

With this
being said, tumour grade must not considered as the only prognostic
factor and should be interpreted in combination with clinical
presentation, WHO stage, additional prognostic markers and
completeness of surgical margins

Equally in RLNs considered within
physiological size histologically detectable metastasis has still been
documented in nearly 50% of cases (Ferrari et al. 2018).

-ve px (high grade):
- rapidly growing, lack demarcation, be ulcerated or cause irritation, present with satellite lesions, or
are associated with paraneoplastic signs
- >3cm
- located on muzzle, mucocutaenous, prepuce, scrotum, vulva
- tumor grade

Histological grading alone is unable to predict the biological
behaviour of each MCT
- mitotic index
- ckit (may be most informative about
histologically low-grade tumours which could be biologically
aggressive)
- Ki067 (not stabdardised across labs) mst useful for grade II tumors

validation of cytological grading is required before its
routine clinical application, but with the information available
at this time, cytology appears reliable in identifying low-grade
MCTs

low grade with l.n. assessment porb don;t need adavnced staging
For MCTs that exhibit the negative prognostic factors
recommended diagnostic tests include, in addition to the above,
abdominal ultrasound plus or minus cytological assessment of
liver and spleen

Answer 39

In recent years, many techniques for mapping
the lymphatic draining of a tumour and to individuate
the sentinel lymph node have been investigated. These include
using contrast-enhanced CT or ultrasound and intra-operative
procedures such as gamma scintigraphy (Worley 2014, Brissot
& Edery 2017, Fournier et al. 2021). Interestingly, in the study
by Fournier et al. clinicians predicting the draining lymph node
of an MCT based on anatomical position were correct in only
54–58% of cases. This suggests lymphoscintigraphy may be suitable
for tumour located in “zones of ambiguity” where the RLN
cannot be easily predicted, for example, MCTs of the head and
neck, and that reliance of lysosome maps of healthy dogs may
not take into consideration the potential for aberrant lymphatic
drainage in the tumour microenvironment (Fournier et al. 2021).

Subcutaneous MCT
The majority of dogs with subcutaneous MCTs have a favourable
prognosis with extended survival times from good local tumour
control and low rates of local recurrence or metastasis
subcutaneous MCTs with an increased Ki-67 (>23)
are significantly more likely to locally reoccur and metastasise

challenges associated with interpretation of MCT
margins Donnelly et al. (2015) demonstrated that regardless of
histologically tumour-free margins in high-grade Kiupel MCTs
there was 36% recurrence rate compared to only 4% in low-grade
tumours.

Question 40

Tigilanol tigilate (TT) is a novel diterpene ester licensed for treatment
of non-resectable, non-metastatic subcutaneous MCTs
located at or distal to the elbow or hock (<8cm3)

Answer 40

TT poses as an attractive alternative treatment
for MCTs in locations that are not amenable to wide surgical
excision or in patients who may have comorbidities that
pose a high risk for general anaesthesia; however, limitations
include the lack of histopathological tumour grading, reported
margins and documented long-term responses.

most suited to stage 0 MCTs that display
traits of being more likely to behave in biologically low-grade
manner.

Question 41

Factors affecting prognosis in canine subcutaneous mast
cell tumors: 45 cases
Nathan L. Cherzan 2023

Answer 41

• recurrence: local 8/45 (17.8%), metastatic recurrence 5/45 (11.1%)
  - local recurrence → MST 551d (80-2050) vs 1722 (10-1722)
  
  • LN metastasis 12/45 (26.7%) → mDFI 194d (18-1864) vs mDFI not reached
    
    • correlated with recurrence, shorter DFI, decreased survival
  • infiltrative tumour → mDFI 268d (3-1722) vs not reached at median 1864d (10-1864)
  • overall MST 1139d
    
    • correlated with mass size (>3cm → 1059d vs <3cm 1722d)
  • more aggressive in this study than previously reported
    
    • previous report: local recurrence 7-9%, metastatic recurrence 2-6%

Question 42

Comparison of indirect computed tomographic
lymphography and near-infrared fluorescence
sentinel lymph node mapping for integumentary
canine mast cell tumors
Alejandro Alvarez-Sanchez 2023

Answer 42

Prospective clinical study.
Animals: Twenty client-owned dogs.
Detection of
ICTL-SLN and NIRF-SLN failed in 1/20 (5%) and 4/20 (20%), respectively
Nineteen out of 20 (95%) dogs had HN2-3 LN.

Technique agreement of at least one SLN was seen in 16/20
(80%) dogs. Although most MCT were classified as intermediate to low grade,
LN metastases were commonly detected.

Lymph nodes containing metastasis would have been
detected in 14/20 (70%) dogs yet missed in 4/20 (20%)
with excision of either the ALN, ICTL-SLN, or NIRFSLN.
The remaining 2/20 (10%) dogs did not have LN
metastasis.

discrepancy reported herein was less
than previously reported.6,11,13 Specifically, in 6/20 (30%)
and 5/20 (25%) dogs for ICTL and NIRF

ICTL and NIRF frequently
detected SLN other than the ALN. As most SLN
in our subset of dogs were metastatic, we caution surgeons
relying exclusively on the ALN for staging considering
the high risk of leaving undetected metastases.

Question 43

Haine 2022 assessment of histological margins for ‘planned narrow excision’ of MCT and STS
using the residual tumour classification scheme (R scheme)

Answer 43

• MCT: 6-10mm measured lateral margins → 7% R1, 0-5mm → 55% R1
  - no association between histologic grade and R1 margins (no high grade in study)

Question 44

Computed tomographic evaluation of the liver showed
no consistent pattern associated with mast cell metastasis and did not predict cytology results.
Multifocal splenic hypoattenuating lesions more commonly coincided with mast cell metastasis.
Sampling of the liver and spleen remains to be considered in the absence of abnormal CT findings
for full staging.

Question 45

Outcome of dogs with intermediate grade low mitotic index high Ki67
mast cell tumours treated with surgery and single agent lomustine
S Nécˇová,* SL Mason and SM North

AVJ

Answer 45

Twenty-one dogs were included. All dogs underwent
surgical excision and two dogs received adjuvant radiotherapy.
None of the patients developed local recurrence. Three dogs
(14.3%) developed metastatic disease. The DFI of these dogs was
141, 186 and 223 days. Median follow-up period of the whole
study population was 1112 days (358–2619). MST for patients
with metastatic disease was 417 days. MST of the whole group
was not reached. One-year and 2-year survivals were 95.2% and
90.5%, respectively.
Conclusions and clinical relevance This study population had
low rates of tumour recurrence and improved survival compared
to previously published data of similar population of dogs with
low MI/high Ki67 MCT without adjuvant chemotherapy.

Question 46

Lymph node metastasis in feline
cutaneous low-grade mast cell
tumours
Raphael Arz 2023

Answer 46

10/17 (59%) cats were affected by nodal metastasis in our population

h cutaneous MCTs that had
undergone lymphadenectomy of enlarged and non-enlarged lymph nodes.

Question 47

Indirect CT lymphography
showed the SLN in 82 of 85 (97%) cases,32%of them not corresponding to the regional
node. CT showed additional or incidental MCTs in 23 of 72 (32%) dogs.

CT is useful in identifying clinically
undetected MCTs and SLNs, although it shows low accuracy in distinguishing between cutaenousMCT and SQMCT.

Answer 47

CT findings were deemed insufficient for curative surgical planning in 13
of 16 due to inadequate definition of tumor depth, compartment boundary (fascial
plane) or MCT margins. The use of CT for presurgical planning of SC/InterM/IntraM
MCT dogs has limitations, especially when differentiating MCT from the adjacent
muscle.

Question 48

Lapsley 2021 – comparison between SLN (assessed by CT-L) extirpation vs cytology on tx
recommendations for cutaneous and subcutaneous MCT

Answer 48

SLN mapping: optimal scan time 10m post-contrast injection
- SLN differed from regional LN in 5/18
- metastasis detected on histology of SLN in 9/20 vs 1/20 cytology → 8/20 change stage/tx

Question 49

Selmic 2020 – systematic review of surgical margins for excision
- low quality evidence but recommendation can be made for excision of Patnaik G1-2 MCT
<4cm diameter with 2cm lateral margins and 1 fascial plane
→ low rate of incomplete excision and local recurrence

Question 50

Guerra 2022 – histologic grade and incomplete margins remain prognostic in Stage IV MCT with
multimodal tx
- median time to progression: high-grade shorter (241d) vs low-grade (not reached)
- tumour specific survival: high-grade shorter (545d) vs low-grade (not reached)