Ch 25 Onocology

Question 1

Generally speaking, what alterations results in the formation of cancer?

Answer 1

Activation of tumour-promoting factors via oncogenes
or
Loss of innate tumour inhibitory effects via tumour suppressor genes (e.g. p53 “guardian of the genome”)

Question 2

What are the phenotypic characterisitics of cancer cells?(6)

Answer 2

Self-sufficiency in growth signals

Insensitivity to anti-growth signals

Tissue invasion and metastasis

Limitless replicative potential > Both human and canine neoplastic tissues have been shown to exhibit high levels of telomerase activity

Sustained angiogenesis

Evasion of apoptosis > Lack of apoptosis is considered a hallmark of carcinogenesis and a key characteristic of cancer cells

tumor suppressor gene p53

Question 3

Oncogenes can be activated by

Answer 3

chromosomal translocation
gene amplification
point mutations
viral insertions

Point mutations can be induced by ionizing radiation and chemical carcinogens or may involve mutations in proto-oncogenes such as K-ras, the epidermal growth factor receptor, and the c-kit growth factor receptor

Question 4

cell division - what the main phases and checkpoints?

Answer 4

interphase
- starts with doubling of genetic material
- GI, G2, and S phases.
- GI and G2 serve as checkpoints that ensure normal DNA synthesis and cell division
- restriction point = critical checkpoint for continued progression of the cell cycle
- S phase = synthesis/doubling of new DNA

mitosis (M)
- division of the doubled genetic material into two daughter cells
- Regulation via proteins called cyclin-dependent kinases

Question 5

Initiation, promotion, and progression of a cell toward a malignant phenotype

Answer 5

applied to genetic factors leading to cancer formation, as well as to chemical carcinogenesis.

Question 6

Which forms of neoplasia have confirmed, true genetic heritability in animals?

Answer 6

Osteosarcoma of Scottish Deerhounds
Renal cystadenocarcinoma in GSD
Nodular dermatofibrosis in GSD

Question 7

List some biologic carcinogens in animals

Answer 7

FeLV and lymphoproliferative diseases

Feline sarcoma virus and FSA (must also be infected with FeLV)

Papillomavirus in puppies. Papilloma can klead to formation of SCC in rare cases

Spircocerca lupi and viral oesophageal sarcomas in dogs

Transmissible venereal tumour by direct cellular transmission

Question 8

List some physical carcinogens (5)

Answer 8

Asbestos and mesothelioma in humans
Injection-site sarcoma in cats
Post-trauma ocular sarcomas
Microchip-associated FSA
TPLO metallurgy and canine OSA

Question 9

List the four possible mechanisms which can transform genes into oncogenes

Answer 9

Oncogenes are mutated versions of normal genes that drive the formation of cancer. The normal counterparts of these genes, called protooncogenes, become transformed by

• Retrovirus-mediated transduction
• Translocation mutation
• Amplification
• Proviral insertion

Question 10

In neoplasia, such as canine mast cell tumor, internal tandem duplication mutations lead to a constitutively active c-kit receptor tyrosine kinase receptor (i.e., ligand binding by stem cell factor is no longer needed for proliferative activity). The c-kit receptor falls under a group of growth factor receptors called platelet-derived growth factor receptors (PDGFRs).

Question 11

Translation of oncogenes leads to transcription of key proteins such as….

Answer 11

Growth factors
Growth factor receptors
Cytoplasmic kinases/Ras
Transcription factors
Antiapoptotic proteins

Question 12

What are Ras oncogenes

Answer 12

Lead to production of membrane-associated proteins that have a key role in cell signalling leading to activation of various cell-proliferative pathways

Question 13

What are the two forms of tumour suppressor genes

Answer 13

Gate keepers - Inhibit growth while promoting cell death (eg. p53)

Care takers - Ensure DNA repair while maintaining genomic stability

p53 is one of the most common mutations. It is crucial for normal cell cycle and serves as a checkpoint for entry into apoptosis

Question 14

Three major routes of metastasis are

Answer 14

(1) hematogenous,
(2) lymphatic, and
(3) direct seeding.

Question 15

In general, how do carcinomas, round cell tumoura and sarcomas metastasise?

Answer 15

Carcinomas and round cell tumours via lymphatics

Sarcomas via haematogenous routes

Question 16

How do metastatic cells survive in their new environment?

Answer 16

Progressive hypoxia due to proliferation (need to be 100-200mcm from capillary bed for continued growth)
Hypoxia activates hypoxia-induced factor (HIF1alpha), an oxygen-dependant transcription factor
HIF-1a induced transcription of tumour-derived growth factos such as VEGF
Growth factors lead to endothelial recruitment and eventual organisation in capillaries

Question 17

Tumor staging is a diagnostic process in which the extent of disease progression from the primary site is determined. The diagnostic tests indicated are dictated by tumor type, so staging is often performed after the tumor type has been determined.

Question 18

What factors need to be considered when choosing a biopsy?

Answer 18

Invasiveness of procedure
Potential for haemorrhage
Seeding of tumour cells
Will it change the treatment plan

incisional biopsy
perform if knowing the specific behavior of a tumor may affect sx treatment or when knowing the identity of the tumor would alter the treatment plan.

excisional biopsy
The main advantage > biopsy and gross tumor removal are performed in a single procedure. disadvantage> if the tumor is highly invasive

Question 19

frozen histologic sections can be performed quickly on samples obtained at the time of surgery, and this information can be used when making intraoperative decisions; however, frozen sections can be prone to sampling error and tissue artifacts.

Question 20

imaging

Answer 20

radiography
three-view (ventrodorsal, left lateral, and right lateral projections) thoracic radiographs to evaluate for pulmonary metastatic

Ultrasonography
evaluation of intra-abdominal neoplasia, particularly hepatic, adrenal, and urogenital tumors, and sublumbar node metastasis.
Guide needles and needle-core biopsy for tissue sampling

CT
evaluation of primary tumors of the axial skeleton, particularly skull, vertebral, and pelvic tumors, and for evaluation of primary and metastatic intrathoracic tumors
3D reconstructions can be manipulated at a computer workstation to help the surgeon
CT-guided biopsy

MRI
preferred for tumors of the central and peripheral nervous system and perhaps intra-abdominal organs.
determining the proximity of tumors to important neurovascular structures ((STIR) MRI)

Question 21

How can nuclear scintigraphy be applied to dogs with OSA? What substance is used for this?

Answer 21

Technetium-99m hydromethylene diphosphate used for a whole body scan to detect aymphtomatic synchronous or asymptomatic lesions

In one study, 7.8% of 399 dogs with appendicular OSA were diagnosed with a second asymptomatic lesion. Not good candidates for amputation

Question 22

List some uses of nuclear scintigraphy

Answer 22

Technetium-99m hydromethyl diphosphate for OSA to detect multiple lesions or to define margins for limb-sparing

Technetium-99m diethylenetriaminepentaacetic acid for GFR prior to nephrectomy

Technetium-99m for thyroid tumours to identify metastatic or ectopic disease

Indium-111 pentetreotide (somatostatin receptor scan) to identify primary and metastatic lesions in dogs with functional insulinomas

Question 23

What is a PET-CT?
What are its limitations?

Answer 23

A radiopharmaceutical (F-fluorodeoxyglucose FDG) is used with is transported into and trapped inside tumour cells because it is not utlised in the glycolic pathway. Signal is higher in tumour cells as they have a higher uptake of glucose

Limitations
- Not all tumours will have increased uptake
- Non-specific (inflammation reacts similarly)
- Not readily available

Question 24

What size metastatic lesions can be seen on thoracic radiographs and CT?

Answer 24

6mm on radiographs
1mm on CT

Question 25

What are the major potential side effects of doxorubicine and cisplatin?

Answer 25

Doxorubicine can cause cardiotoxicity
Cisplatin can cause nephrotoxicity

Question 26

What are the 4 categories of tumour excision?

surgical dose

Answer 26

Debulking
Marginal
Wide
Radical

Question 27

Perioperative Management

Answer 27

Comorbid Conditions
Chemotherapy, radiation therapy, and/or surgery can be altered, incorporated, or eliminated on the basis of comorbid conditions

Pain and Analgesia
Tumor-associated pain

Question 28

Wide and Radical Resections

provides the best chance for cure

Answer 28

considered curative-intent surgeries because the intention is to resect both macroscopic and microscopic disease, including biopsy tracts, and thus prevent local tumor recurrence and improve overall survival times

evidence suggests that tumor size also influences the extent of microscopic tumor extension, with larger tumors of the same histologic type having greater microscopic extension and hence requiring larger margins than smaller tumors. 28 Margins are three-dimensional; hence, lateral and deep margins must be considered when planning surgical resections of tumors

Deep margins are determined by natural tissue barriers because deep margins (1 to 3 cm) may not be possible
> muscle fascia
> cartilage
> bone
are resistant to neoplastic invasion and provide a good natural tissue barrier

Radical resection, which is defined as the removal of an entire tissue compartment

The deep margin is the most common site of failure.

Question 29

What are the general rules for lateral margins of soft tissue sarcomas, MCT and carcinomas

Answer 29

Sarcomas and MCT - 2-3cm lateral margins

Carcinomas - 1cm usually sufficient

Question 30

A study by Simpson et al revealed what regarding lateral margins for MCT excision?

Answer 30

All grade 1 MCT were completely excised with 1cm margins

Only 75% of grade 2 MCT were completely excised with 1cm margins, increasing to 100% with 2cm margins

2cm margins recommended for grade 1 and 2, not enough data to make recommendations for grade 3 so should aim for 3cm if possible

Question 31

Marginal resection

Answer 31

is performed by dissecting just peripheral to the tumor pseudocapsule in the reactive zone

malignant neoplasms, this approach usually fails due to failure to remove microscopic satellite tumor cells

Planned marginal resection, when combined with postoperative radiation therapy

Question 32

What are the 4 options when incomplete excision is achieved?

Answer 32

1. No treatment
2. Staged resection of the scar
   Staging resection therefore can be used to determine whether animals need to be subjected to additional expensive, time-consuming > xcision of the surgical wound with ≤10-mm margins
3. Wide scar revision
4. Combination with radiation or chemo

78% of STS reported as incompletely excised do not have any evidence of residual tumour following further resection

Question 33

Is LN size a predictor of mets? Give an example from the literature

Answer 33

No
A study of 100 dogs with oral malignant melanoma, 40% of dogs with normal-sized LN had metastasis and 49% of dogs with enlarged LN did not have metastasis

Question 34

sentinel lymph node

Answer 34

• based on the theory that the metastatic process occurs in an orderly progression within the lymphatic system, with tumor cells draining into a specific lymph node (i.e., the sentinel lymph node) in a regional lymphatic field before draining into other regional lymph nodes.
• The sentinel lymph node has an important role as a filter and barrier for disseminating tumor cells.
• distant metastasis should not be present if the sentinel lymph node does not have evidence of a tumor burden

Question 35

List some methods of identifying the sentinel lymph node (4)

Answer 35

lymphoscintigraphy
peritumoral injection of blue dye,
intraoperative cytology/histopathology
Idocyanine green fluroscence

Question 36

Lymph Node Dissection

advantage is that of cytoreduction

Answer 36

Halsteads
theory of “contiguous” development of metastases, surgeon would remove the primary tumor and the draining regional lymph node if it is known to contain tumor cells with the expectation it preventing spread to the next lymph node in the chain or systemically

Cady-Fisher view
cancer is a systemic disease, and that lymphadenectomy, does not affect survival.
cancer cells are assumed not to spread in an orderly manner, and regional lymph nodes are viewed ineffective barriers > biologic indicators of cancer spread that merely guide therapy and prognosis

Question 37

What are some considerations regarding surgical technique for oncologic surgeries? (7)

Answer 37

Early haemostasis to prevent release of tumour emboli

Careful handling to prevent exfoliation

Structures adhered to the tumour should be resected en bloc if possible (57% rate of invasion in humans)

Not Multifilament > associated with an increased risk of recurrence

Ideally avoiding drains as can extend margins if resection if incomplete

Reconstructive surgery is ideally done as a second procedure once histology results have confirmed clean margins

Gloves and instruments changes prior to closure or between mass removals

Question 38

What IHC markers are used for carcinomas and sarcomas?

increasingly malignant, cells become increasingly similar histologically

Answer 38

Cytokeratin (found in epithelial calls) stain for carcinomas

Vimentin (found in mesenchymal cells) stain for sarcomas (and melanoma)

immunohistochemistry can help determine the cell of origin

poorly differentiated tumors commonly lose expression of these markers

Question 39

margins

clean but close —in one study in soft tissue sarcoma, this was described as tumor cells found within 1 to 3 mm of the margin.

Descriptions such as “tumor is close to the margins” or “tumor cells do not appear to extend to the margins of the excision” > Whether or not this is classified as a clean margin depends on the tumor grade (low vs. high) and also on the surgeon’s interpretation

Question 40

pathology samples is tissue shrinkage

Answer 40

oral surgery in healthy dogs
- mean shrinkage of tissue from initial resection to final microscopic assessment ranged from 30.7% to 47.3%
- reatest proportion of shrinkage occurred immediately upon resection, with further shrinkage noted once fixed in formalin.
- obtain 5 mm of pathologically clear margin, an in situ margin of resection of at least 8 to 10 mm needs to be taken
- normal dog skin, fixed in formalin and then processed, have been shown to decrease in length and width by as much as 32% and to increase in thickness by 75.8%

Question 41

What to Do With Incomplete Margins

ability to predict behavior of tumor of one individual is less clear

Answer 41

i.e. phenomenon of local recurrence after wide tumor negative margins have been achieved or following wide resection of scars containing too few tumor cells to even be detected histologically.

Positive microscopic margins following soft tissue sarcoma > 0.5 times increased risk of local recurrence

wait and see > A low recurrence rate of mast cell tumors has been described after incomplete excision of grade 2 mast cell tumors, and the recurrence rate following intentional marginal excision of low-grade sarcomas on the extremities was only 11% in one study

Question 42

MCT recurrence rate

Answer 42

• recurrence rate following complete surgical excision of grade 2 mast cell tumors is 11%
• only 18% to 35% of incompletely excised grade 2 mast cell tumors recur.

Question 43

What proliferation markers can be used to help predict recurrence of incompletely excised grade 2 MCT?

Answer 43

Ki67 (low vs high have signifcantly prognosis)

Proliferating cell nuclear antigen (PCNA) combined with Ki67 is prognostic for recurrence

Question 44

What are the advantages of neoadjuvant radiation therapy vs adjuvant radiation therapy

Answer 44

Neoadjuvant
- (prior to surgery) is theoretically more effective due to unimpaired vascular supply (better oxygenated, less hypoxic and therefore more radiosensitive)
- Irradiated skin is more likely to develop incisional complications

Adjuvant radiation
- can also increase incisional complications, especially if started before 7 days post-op
- Radiation is much more effective against microscopic disease and there is no delay in surgery with adjuvant radiation

Question 45

For dogs with soft tissue sarcoma, adjuvant (postoperative) radiation therapy is much more effective against microscopic disease, with 1-year disease-free control rates >95% for residual microscopic disease and only 50% for dogs with macroscopic tumor burden

Question 46

Cell Kill

VAT, PAD, BIT

Answer 46

chemotherapeutics kill rapidly dividing cells in a nonselective manner.
Rapidly dividing cells include neoplastic cells + epithelium of the gastrointestinal tract and bone marrow, hair

Cell cycle–specific drugs refer to those that are in the synthesis (S) or M phase of the cell cycle

Non–cell cycle–specific drugs are capable of cytotoxicity in any phase of the cell cycle

Question 47

timing of chemo

Answer 47

chemotherapy is administered in the adjunctive setting, usually starting at 10 to 14 days postoperatively to allow for adequate healing and recovery.

risk of wound complications is low because this allows wound fibroplasia and neovascularization to begin while still maintaining a favorable environment for the antineoplastic effects of the chemotherapy agents, such as low tumor burden and few drug-resistant cells.

Question 48

Define “maximally tolerated dose” chemotherapy

Answer 48

Chemotherapy where toxicity, dosage and interval of treatment are base on phase I clinical trials . This data is not often available for vet patients and is extrapolated from human date. Drug doses delivered in vet med are typically half that in humans

Question 49

Define metronomic chemotherapy

Answer 49

Frequent, even daily, administration of chemotherapeutics at doses significantly below maximally tolerated dose, with no prolonged drug-free breaks

Aims to control or minimise angiogenesis and invasion rather than cytotoxicity

Question 50

Alkylating agents

Answer 50

• Non cell cycle specific
• inserting bulky alkyl groups onto DNA/RNA strands, leading to interference in DNA replication and RNA translation.
• Loumustine (Histiocytic sarcoma, MCT). Severe hepatotoxicity 6%
• Cyclophosphamide (lymphoma). Furosemide can reduce occurence of sterile haemorrhagic cystitis

Question 51

Doxorubicin

Answer 51

• non cell cycle specific
• multiple mechanisms of action: topoisomerase inhibition, DNA intercalation, and formation of iron-mediated free radicals that lead to DNA damage.
• Lymphoma, HSA, high grade STS, high grade carcinoma, OSA
• Can cause DCM like damage in dogs, renal insufficiency in cats
• Significant myelosuppression and GI toxicity

Question 52

Platinum agents

Answer 52

• Non cell cycle specific
• caused covalent binding of DNA, restricting replication and protein systhesis
• Carboplatin and cisplatin - OSA, rescue for other sarcoma and carcinomas
• Cisplatin fatal to cats! Fatal pulmonary oedema
  Nephrotoxicity

Question 53

Microtubule inhibitors (Vinca Alkaloids and Taxanes)

Answer 53

• Cell cycle specific
• affect spindle apparatus during mitosis
• Vincristine (lymphoma)
• Vinblastine (MCT)

Minimally myelosuppresive and well tolerative. Can cause paralytic ileus and extravasation phlebitis

Question 54

Bisphosphonates

Answer 54

Inhibits osteoclast activity - palliative Tx for osteolytic disease from OSA, multiple myeloma and metastatic bone disease
IV is preferred (low oral bioavailability, cause reflux)
Pamidronate most common - approx 30% successful palliation
Zoledronate - shorter infusion time, improved inhibition or resorption (100x potency), potential for less frequent treatment

Question 55

tyrosine kinase inhibitor

Answer 55

• inhibits tyrosine kinases.
• important mediators of gene transcription and are key to cell proliferation, as well as tumor growth and survival
• targeting the ATP binding sites of membrane and cytoplasmic tyrosine kinases that are crucial for phosphorylation

toceranib
- targets the tyrosine kinase, c-kit, which is often mutated in dogs with high-grade mast cell tumor
- Indicated for high grade or metastatic disease and work best on microscopic disease

Question 56

What are the reported morbidity and mortality rates of chemotherapy patients as a whole?

Answer 56

15% require nonhospitalised medical attention
5% hospitalised
1% mortality rate

Question 56

What is the most available form of immunotherapy?

Answer 56

Melanoma vaccine

DNA vaccine utilising human tyrodinase DNA which shows an unregulation of antibodies in dogs against human tyrosinase. Clinical studies show mixed efficacy…

Question 57

When is the bone marrow nadir with chemotherapeutics?
At what level is chemo delayed?

Answer 57

Typically approx 7 days with the exception of carboplatin which is approx 10-14 days

Chemo is delayed by 5-7 days if neutrophils are less than 1500-2000/mcL and platelets less than 50,000/mcL

If neuts under 1000, prophylactic ABx initiated and future doses reduced by 20%

Question 58

What is the most common mechanism of acquired chemotherapeutic resistance?

Answer 58

Mutation in the canine MDR-1 gene (Collies, Shelties, Australian Cattle Dogs may already have this mutation)

Question 59

Neoadjuvant chemotherapy and radiation therapy in veterinary cancer treatment: a review
B. Wustefeld-Janssens

Answer 59

limitations of neoadjuvant therapy
the results of neoadjuvant therapy in both human and veterinary oncology are overall equivocal except for the specific
examples cited above. Often, the benefits of neoadjuvant therapies that may target a large portion of cells, yet leave behind a
relatively resistant fraction of cells are mitigated by early use in the disease process.

The decision to use neoadjuvant therapy can be made to improve
the probability of a negative resection or reduce morbidity of
surgery in borderline resectable disease

cutaneous mast cell tumours in dogs
where the use of prednisone in the neoadjuvant setting has
been shown to be beneficial.

The largest randomised controlled trial addressing
the question of NRT versus adjuvant RT in extremity sarcoma
found that the surgical site complication rate was doubled in
patients that had NRT

study examining the tolerance of cutaneous or mucosal flaps
placed in a radiation field in dogs (Seguin et al. 2005). The risk
of complications were 19 times higher in dogs that had a flap as
part of a salvage procedure for previously irradiated tumour and
the severity of complications were increased in higher doses per
fraction.
previously irradiated required a flap for salvage. Flaps are inherently
at a higher risk for ischemic necrosis and dehiscence

Question 60

The studies concerning evaluation of COX-2 expression in animals revealed its overexpression in various types of canine and feline tumours found in the skin, mammary gland, urinary bladder, intestines, and bones

Question 61

Sentinel lymph node detection differs when comparing
lymphoscintigraphy to lymphography using water soluble
iodinated contrast medium and digital radiography in dogs
Hlusko 2020

Answer 61

prospective, method comparison study was to compare
an SLN mapping protocol of lymphoscintigraphy to lymphography

An SLN
was identified in all dogs with lymphoscintigraphy and seven of eight dogs with lymphography.
Agreement between results of the lymphoscintigraphy and lymphography
studies was a completematch in three dogs, a partial match in four dogs, and nomatch
in one dog. The SLN detected differed based on the imaging modality used.

Question 62

Diffusion weighted magnetic resonance imaging is a feasible
method for characterizing regional lymph nodes in canine
patients with head and neck disease
Stahle 2019

Answer 62

The objective of this prospective,
exploratory study was to evaluate diffusion-weighted MRI and ADC as potential methods for
detecting metastatic lymph nodes, eight client-owned canine

hypothesis that mean ADC values would
differ between benign and metastatic lymph nodes was not supported.

Lymph node size alone is suggested to be
insufficient for accurate clinical staging of diseases such as canine
oral melanoma, because normal sized lymph nodes may contain
microscopic metastatic disease and lymph node enlargement can
occur in absence of metastasis. Cytologic or histologic examination of
the regional lymph nodes is therefore recommended

Williams Association between lymph node size and metastasis in dogs with oral malignant melanoma: 100 cases (1987– 2001). J AmVet Med Assoc. 2003;222:1234–1236.

Question 63

Lymphadenectomy improves outcome in dogs with resected Kiupel high-grade cutaneous mast cell tumours and overtly metastatic regional lymph nodes
C. Chalfon 2022

no sentinal ln mapping??

Answer 63

retrospec, Forty-nine dogs were included, 18 did not undergo lymphadenectomy while 31 underwent lymphadenectomy

Dogs with a cytological diagnosis of regional lymph node metastasis that did not undergo lymphadenectomy were compared with dogs that underwent lymphadenectomy and had a histological diagnosis of overt lymph node metastasis

Median time to progression was significantly shorter in dogs that did not undergo lymphadenectomy (150 days compared to the other dogs (229 days.
Median survival time was also shorter in dogs that did not undergo lymphadenectomy (250 days compared to dogs that underwent lymphadenectomy (371 days

It is widely accepted that canine cMCTs metastasise in a stepwise
manner from the primary tumour to the draining LN/s and
then systemically to distant sites (Warland et al. 2014).

dogs received adjuvant medical treatment,
protocols were not standardised

lymphadenectomy
along with the resection of the primary tumour and adjuvant
medical treatment improves outcome for dogs with K-HG
cMCTs and overt nodal metastasis.

Question 64

Near-infrared fluorescent image-guided
lymph node dissection compared with
locoregional lymphadenectomies in
dogs with mast cell tumours
beer 2022

Answer 64

retrospectively, Thirty-five patients underwent near-infrared fluorescent image-guided lymph node dissection, and 43 lymph node dissections

Fifty-eight of those (83%) were identified during near-infrared fluorescent imageguided
lymph node dissection procedures, compared with 50 (74%) during lymph node dissection.

fluorescent nodes not corresponding to locoregional nodes in 15 of 35 dogs

suggests that near-infrared imaging is a promising technique for intraoperative detection of the draining lymph nodes in dogs with mast cell tumours. Further validation of the technique is required to assess if near-infrared fluorescent imaging can detect the true sentinel
lymph node.

deep nodes will be missed if these techniques are used without
additional lymphoscintigraphy or CT-based SLN mapping. Ferrari et al. (2020, 2021) reported direct drainage to a medial iliac lymph node in only one of 57 nodes (1.7%) in dogs with MCT

Indocyanine green-based near-infrared fluorescent imaging has been demonstrated
to be the most reliable single technique to identify SLN in the head and neck region of dogs (91%) (Wan et al. 2021)

Question 65

More than two-thirds (69%) of patients treated by NIR-LND
had one or more metastatic lymph nodes. This rate of affected
patients was slightly higher than reported in other studies that
performed SLN mapping using lymphoscintigraphy and methylene
blue dye (12 of 19, 63%; Worley 2014) contrast-enhanced
ultrasound (21 of 35, 60%; Fournier et al. 2021) or indirect
CT lymphangiography (9 of 16, 56%; Lapsley et al. 2021).

Question 66

Influence of locoregional lymph node aspiration cytology vs
sentinel lymph node mapping and biopsy on disease stage
assignment in dogs with integumentary mast cell tumors
lapsley 2021

Previous studies in which scintigraphy was employed to identify the SLN have provided evidence that the SLN may differ from the LRLN in 40% of tumors.

Answer 66

Seventeen dogs undergoing primary excision of 20 cutaneous and
subcutaneous mast cell tumors (MCT).

Mast cell tumors were graded as 2 low (n = 11), 2 high (n = 2), and
subcutaneous (n = 7). Optimal scan timing was 10 minutes after injection of
iopamidol. Sentinel lymph node differed anatomically from LRLN in 5 of
18 scans. Metastases were detected by histology in 9 of 20 SLN compared with
in 1 of 20 FNA of LRLN

Only 6 of 19 LRLN FNA samples were
diagnostic.

Sentinel lymph nodes were consistently identified with ICTL and differed from LRLN in one-quarter of tumors. Histopathological examination of SLN altered recommendations in half of the dogs compared with the previous standard of care.

Should have excised both the LRLN and the sentinel LN rather than comparing cytology to histology

Whether SLN excision and histopathology confer a survival advantage over LRLN excision or cytology that compensates for the imaging costs and increased surgical time remains to be determined.

Question 67

The combination of low sampling success together with a previously reported 75% sensitivity of FNA cytology for identifying positive nodes in MCT disease brings in to question the advisability of using this technique in guiding treatment decisions

Question 68

Biopsy of sentinel lymph nodes after injection of methylene
blue and lymphoscintigraphic guidance in 30 dogs with
mast cell tumors
Roberta Ferrari 2020

Answer 68

Clinical prospective cohort study

Sentinel lymph node mapping was applied to 34 MCT in 30 dogs without any complication. Sentinel lymph nodes were not identified in three of 34 tumors, all with previous scar tissue. Sentinel lymph nodes did not correspond
to expected RLN in 19 of 30 (63%) tumors. Histological examination confirmed an early or overt metastasis in 32 of 57 (56%) SLN extirpated.

Question 69

Reductions in margin length after excision of grade II mast cell
tumors and grade I and II soft tissue sarcomas in dogs
Milan Milovancev 2018

Answer 69

resected canine mast cell tumors (MCT) and soft tissue sarcomas (STS) between the
time of collection and histopathology.
Study design: Prospective, hypothesis-driven, clinical study.
Sample population: Two hundred and thirty-seven margins from 69 excised tumors
(50 MCT and 19 STS) in 51 client-owned dogs.

was reduced by a median of 3.0,
5.0, 6.0, and 8.8 mm for MCT; 2.5, 2.0, 5.0, and 5.0 mm for STS. All processing steps
resulted in significant reductions

Surgical margin length reductions occur due to a combination of physical
factors (eg, tissue elasticity, myofibril contraction, and histologic processing) and
biological factors (eg, microscopic tumor infiltration into the grossly normal surgical
margin)