Surgical oncology Flashcards
What are the phenotypic characteristics of neoplasia?
- Self sufficiency in growth signals
- Insensitivity to anti-growth signals
- Tissue invasion and metastasis
- Limitless replicative potential
- Sustained angiogenesis
- Evasion of apoptosis
What can activate oncogenes?
Chromosomal translocation, gene amplification, point mutations and vital insertions
What are the stages of cell progression toward a malignant phenotype?
Initiation, promotion, progression
What are the only neoplasms with established heritability in dogs?
Osteosarcoma in scottish deerhounds, renal cystadenocarcinoma and nodular dermatofibrosis in German shepherds
What is an oncogene?
A mutated version of a normal gene that drives the formation of cancer
What are the main classes of proteins that translation of oncogenes lead to the transcription of?
Growth factors, growth factor receptors, cytoplasmic kinases/Ras, transcription factors, antiapoptotic proteins
What is the mechanism of action of Toceranib (Palladia)?
It is a tyrosine kinase inhibitor. This is used in dogs exhibiting mutation of the c-kit receptor which leads to a constitutively active c-kit receptor tyrosine kinase receptor and increased proliferative activity
What is the ‘two-hit hypothesis’?
For mutations in tumor suppression genes to occur both alleles need to be damaged
What are the two groups of tumour suppression genes?
Gatekeeper and caretaker
Mutations of what tumour suppression gene have been identified as a prognostic factor for osteosarcoma and canine mammary tumours?
p53 gatekeeper gene
Do canine neoplastic tissues express increased or decreased levels of telomerase activity?
Increased - potentially leading to increased replicative potential. Telomerase is responsible for adding sequences onto the end of telomeres which undergo shortening with each cellular replication (end replication problem)
What are the three major routes of metastasis?
Hematogenous, lymphatic, direct seeding
What is the most common route of carcinoma and round cell tumour metastasis?
Lymphatic
What is the most common route of sarcoma metastasis?
Hematogenous
What type of ultrasonography can be useful in differentiating between benign and malignant splenic neoplasms?
Enhanced harmonic ultrasound
What are the common oncologic indications for nuclear scintigraphy?
Diagnosis of osteosarcoma metastasis, identification of ectopic or metastatic disease with functional thyroid tumours, assessment of GFR prior to nephrectomy (all technetium 99), or somatostatin scans to assess for metastatic lesions in dogs with functional insulinomas
Does CT or MRI have higher contrast resolution?
MRI
How does PET (positron emission tomography) work?
F-fluorodeoxyglucose (FDG) is administered and is taken up preferentially by tumour cells (typically higher glucose metabolism). It is trapped inside tumour cells following uptake as it is not utilized in the glycolytic pathway. Can be combined with CT scan (PET-CT) for anatomic and physiologic information.
What size metastatic lesions can thoracic radiography and CT scans detect?
Radiography: 6mm
CT scan: 1mm
What does the TMN system of tumour classification stand for?
Tumour, node, metastasis
To what organ is doxorubicin toxic?
Cardiotoxic
To what organ is cisplatin toxic?
Nephrotoxic
What are the surgical doses of tumour excision?
Intralesional (debulking), marginal, wide, radical
What are the commonly recommended lateral margins for carcinomas, sarcomas and benign tumours?
Benign: 1cm
Carcinomas: 1cm
Sarcomas: 2-3 cm (1cm may be adequate for low grade tumours)
What are the recommendations for lateral margins in canine mast cell tumours?
Can consider proportional margins for small or low grade tumours (recurrence in only 1/40 dogs in study with predominantly low grade tumours).
Simpson et al: 1cm may be adequate for grade 1 tumours, 2cm for grade 2 (only 75% of grade II tumours completely excised with 1cm margins, 100% with 2cm).
High grade tumours recommend 3cm, although no definitive literature
What tissues constitute an adequate deep margin?
Bone, cartilage, fascia
What is generally responsible for tumour recurrence following marginal excision with a malignant neoplasms?
Microscopic satellite tumour cells that exist outside the tumour capsule
What are the four potential techniques to manage unplanned marginal resections that result in incompletely excised malignancies?
- No treatment
- Staging resection of the surgical wound
- Wide resection of the surgical wound
- Combination with radiation therapy or chemotherapy
With staging resection of the surgical wound what percentage of soft tissue sarcomas had no evidence of residual tumour despite initial incomplete excision?
78%
Is lymph node size an accurate predictor of metastasis?
No - in 100 dogs with malignant melanoma 40% of dogs with normal sized LNs had metastasis, and 49% with enlarged LNs did not
In what percentage of dogs was concurrent tumour excision and axial pattern flap reconstruction associated with incomplete excision in one study?
39%
Describe the anatomic landmarks for identifying the superficial cervical, axillary, and superficial inguinal lymph nodes as per Worden 2023 in JAVMA.
In a study by Beer 2022 in JSAP, what percentage of lymphadenectomies for mast cell tumours in dogs performed with NIRF identified a metastatic lymph node compared to without?
With NIRF 68% of dogs had one metastatic node detected, without only 33%.
In a study by Manfredi 2021 in VRU, what percentage of dogs had a sentinel lymph node detected by lymphoscintigraphy? What agent was used for detection? What was the agreement rate between the SNL on lymphoscintigraphy and expected regional lymph node?
95% of dogs had a sentinel lymph node successfully identified.
Technetium 99 was used for detection.
The agreement rate between regional lymph node and lymphoscintigraphy was 61%.
In a study by Weston 2021 in VRU, what were two distinguishing features of canine pleural/peritoneal sarcomatosis and carcinomatosis on physical examination and CT?
Dogs with sarcomatosis tended to be heavier than dogs with carcinomatosis (due to prevalence of hemangiosarcoma). Peritoneal effusion was more likely in dogs with carcinomatosis.
Significant overlap was observed in both dogs and cats based on imaging findings and therefore histology recommended to definitively delineate disease.
