Oncology 1.0 Flashcards
what is cancer?
uncontrolled proliferation of abnormal cells independent of normal homeostatic mechanisms and the requirement for new cells
what are the reasons a patient may die of cancer?
delayed/incorrect diagnosis
failure of treatment
owner decided not to treat
what are the AVMAs signs of cancer?
abnormal swelling that persists/continuously grows
sores that don’t heal
unexplained weight loss
loss of appetite
bleeding/discharge from any body opening
bad odour (especially halitosis)
difficulty eating/swallowing
reluctance to exercise/loss of stamina
difficulty breathing, urinating, defecating
change in behaviour
what is the most common neoplasia seen in dogs?
mast cell
what is the use of cytology for neoplasia?
guiding diagnostics and treatment planning particularly prior to surgery
what is the use of histopathology for neoplasia?
making a final diagnosis and guiding post surgical treatment
when is needle off FNA used?
lymph nodes
suspected round cell tumours
when is needle on FNA used?
suspected solid tumours
needle off gave a poor yield
what are some tips for needle on FNA?
don’t go through lesion
be vigorous
release suction before taking needle out
what are some contraindications of sampling/biopsy of neoplasms ?
risk of bleeding - evidence of coagulopathy
risk of pneumothorax, urine, abscess leakage after sampling
risk of tumour transplantation deeper into tissue (seeding)
damage adjacent structures
what are some issues associated with FNAs?
not always diagnostic
not always representative - heterogenous or healing lesions
what are the advantages of needle core biopsies?
larger sample than aspirates
inaccessible tissue can be assessed percutaneously
can evaluate some architecture
can do conscious but sedated
what is the most commonly used technique for an incisional biopsy?
inverted wedge
what are the general rules for incisional biopsies?
avoid major structures
avoid necrotic, haemorrhagic, infected areas
should be able to remove entire biopsy tract in subsequent surgery
general rules of surgery
ensure adequate fixation when removed
include normal tissue if able to
what tumours are surface pinch/grab biopsies often used for?
nasal tumours
what is the technique point to note when doing a punch biopsies?
rotate punch continuously the same direction to ensure you don’t shear the layers
what cases is excision biopsy appropriate without pre-treatment diagnosis?
haemorrhagic splenic mass
mammary tumours
pulmonary tumours
what are some contraindications for excision biopsies?
rapidly growing masses
ill-defined/poorly demarcated lesions
peritumoural oedema or erythema
skin ulceration
injection site mass in cats
suspicious of MCT or STS after FNA
non-diagnostic FNA
when is the only time active monitoring should be considered?
if a diagnosis has been made and owners have been made aware of this
what system is usually used to stage solid tumours?
TNM classification
what is the TNM classification for staging solid tumours?
T - primary tumour
N - metastatic disease in local lymph nodes
M - distant metazoic disease
how is clinical staging of T (primary tumour) carried out?
clinical examination
location and palpability
fixation - deeper tissue, skin…
is ulceration present
imaging (plain/contrast radiograph…)
advanced imaging (CT, MRI…)
what are the two categories of metastatic patterns?
haematogenous
lymphatic
what two tumours commonly metastasis haematogenously?
sarocomas
malignant melanoma
how is clinical staging of N (nodal metastasis) carried out?
palpation (lymph node size, texture…)
imaging (radiography, ultrasound, lymphangiography…)
cytology/histology (FNA, biopsy…)
what is lymphangiography?
injecting contrast into a tumour to determine which node it drains to (CT based)
what lymph node do cranial abdomen tumours metastasise to?
sternal lymph node
what lymph node do thyroid carcinomas metastasise to?
retropharyngeal lymph nodes
what are common sites of metastatic disease?
lung
parenchymatous organs
bone
skin
CNS
distant nodes
what is a cause of mineralised opacities in the lungs that look like metastasis?
pulmonary osteoma
what are the indications for cytology?
lesion - palpable or seen on imaging
organomegaly
cavitary effusion
cancer staging - lymph nodes, liver, spleen
pyrexia of unknown origin
what is usually used to stain cytology slides for analysis of tumours?
diff quik (wear gloves and dip 10 times in each)
what are the stages of analysis a cytology slide of a tumour?
assess with naked eye
low magnification
what is assessed by the naked eye on cytology slides of tumours?
is it labeled
macroscopic appearance - good staining, even distribution
what is assessed on low magnification of tumour cytology slides?
intact cells
cellular populations
thin regions with good nuclear/cytoplasmic detail
what do lots of ruptured cells suggest about the cytology slide?
incorrect sampling/smearing (repeat sampling procedure)
why might a cytology slide have inadequate staining?
insufficient time in stain
inadequate drying time
layer of cells is too thick
exposed to formulin fumes
what are the predominant cell types seen with inflammation?
neutrophils, macrophages, lymphocytes, plasma cells, eosinophils
(can also see microorganisms)
what are the three types of cells seen with neoplasia?
epithelial (skin, gut, glandular…)
mesenchymal (connective tissue, muscle…)
round cells (immune system)
once you have identified neoplasia on cytology what should be assessed next, starting from low power?
cell arrangement - cohesive, cytoarchitecture…
cell shape - round, spindle, polygonal…
how can the cell arrangement/shape of epithelial cell neoplasms be described?
cohesive - adhere in clumps/clusters
well define cell-cell junction
polygonal, cuboid, columnar with round nucleus
how can the cell arrangement/shape of round cell neoplasms be described?
non-adherent and individualised
round with round/oval nuclei
how can the cell arrangement/shape of mesenchymal cell neoplasms be described?
non-adherent but can be loosely aggregated
fusiform to stellate shape with elongated nuclei
wispy cytoplasmic projections
indistinct cell borders
are most skin tumours in dogs and cats benign or malignant?
cats - malignant
dogs - benign
what are some examples of round cell tumours?
histiocytoma
plasma cell tumour
mast cell tumour
lymphoma
(transmissible venereal tumour)
what are some non-neoplastic non-inflammatory lesions?
keratinising cysts (sebaceous cysts)
sebaceous hyperplasia
what are the two groups of criteria of malignancy?
nuclear criteria (stronger indication)
cytoplasmic criteria
what are the nuclear criteria of malignancy?
mulitnucleation
karyomegaly
mitoses
nuclear moulding
large, angular, variably sized nucleoli
what is the minimum number of criteria of malignancy to suggest a malignant neoplasm?
minimum of three throughout the smear (take into account organ/cell type)
what are the two main categories of radiotherapy?
brachytherapy (radiation close to tumour)
tele therapy (radiation far from tumour)
what are the types of brachytherapy?
direct application
implantation
systemic administration
what is the main type of teletherapy?
external beam (linear accelerator)
what are the ways radiation is produced for teletherapy?
linear accelerator
natural radioactive decay
what are the main forms of therapy used in teletherapy?
photon and electrons produced by linear accelerators
what is the Compton effect?
when a photon interacts with another molecule (usually electron) there will be release of energy from the electron and the photon will have slightly more energy (hence the maximum dose isn’t absorbed at the skin but builds up)
what piece of equipment is needed to treat the skin with teletherapy?
bolus (allow compton effect before it hits the skin) - skin can achieve maximum dose
what is the indirect way high energy electromagnetic radiation damages DNA?
water molecules are ionised which generates free radicals which cause damage to DNA
why do photons not cause much direct damage to the DNA?
DNA is very small so chances of photon hitting it is very small
what inhibits the rapid repair of DNA?
oxygen (hypoxic cells DNA repaired quicker)
how much more radiation is required to kill a hypoxic cell than a well oxygenated cell?
3 times
how can high energy electromagnetic radiation cause cell death?
induce apoptosis
permanent cll cycle arrest
mitotic catastrophe
why might the full effects of high energy electromagnetic radiation therapy not be seen until weeks later?
cell damage often isn’t expressed until the cell tries to divide, at this point the damage becomes apparent and the cell dies
is single or multiple beam radiation therapy generally better?
multiple - increase tumour dose while sparing surrounding tissue
what type of tumours are electrons usually used to treat?
superficial tumours (skin) - lose energy rapidly as it passes through tissue
what are the four Rs of response radiotherapy?
repair
repopulation
redistribution/reassortment
reoxygenation
what is fractionation in relation to radiotherapy?
total dose of radiation required to kill cells is less if a few larger doses is given rather than lots of smaller doses
what tissues is repopulation in response to radiotherapy seen most commonly in?
rapidly dividing tissues (slightly protects normal tissues)
what is the redistribution response to radiotherapy?
certain stages of the cell cycle are more sensitive to radiation than others (late G2 and M sensitive) so cell cycle can become synchronised after one treatment (use multiple treatments)
how can redistribution response to radiation therapy be used to our advantage?
cells synchronise there cycle as certain stages are more effected by radiation so can treat a second time to damage more cells
why is one larger radiation dose more effective than multiple smaller doses?
cells have time to repair between therapy
cells can repopulate between therapy
why would fractionation be beneficial?
allows normal cells to repair and repopulate
what are the limitations of fractionation in animals?
requires GA
cost
owner compliance
are cats or dogs better at dealing with radiation therapy side effects?
cats (dogs don’t deal well)
what cell cycle phase is the most resistant to radiotherapy?
S - synthesis phase (new DNA being made)
what cell cycle phase is the least resistant to radiotherapy?
M - mitotic (cell dividing)
why are smaller tumours more sensitive to radiotherapy?
rapidly dividing
high fraction of cells in sensitive growth phase
better oxygenation
can dose evenly and accurately
what are some tumours that are very sensitive to radiotherapy?
lymphoma
transmissible venereal tumour
gingival basal cell carcinoma
what are some tumours that are very resistant to radiotherapy?
fibrosarcoma
haemangiopericytoma
oral SCC (cats)
osteosarcoma
rhinarial SCC (dogs)
what are some acute side effects of radiotherapy?
rapidly dividing cells - skin and MM (erythema or desquamation)
what are the late side effects of radiotherapy?
damage to tissue/microvasculature - ischeamic necrosis, alopecia, skin fibrosis, reduced healing capacity