Oncology Flashcards
What 6 features are necessary for the development of cancer?
Self-sufficiency in growth signals Insensitivity to anti-growth signals Tissue invasion and metastasis Limitless replicative potential Sustained angiogenesis Evading apoptosis
How does alteration in genes cause cancer?
Overactive oncogens (tumour-promoting genes) - secondary to mutation Loss of tumour suppressor genes
Define neoplasia/neoplasm.
‘New growth’, but inferring abnormal growth
Define benign.
Neoplasm that forms a solid cohesive tumour and does not metastasise
Define malignant.
Neoplasm with the capacity for local invasion and metastasis
What are the important clinical features of a cancer?
Effect on the host
Response to treatment
Reflection of tumour growth/grade/behaviour
When is it possible to detect a tumour by palpation/radiography?
When approx. 1cm in diameter / 1g in weight / 10^9 cells
Tumour does most of its growing before detection
Define ‘growth fraction’.
Growth of a tumour is a function of the proportion of actively dividing cells.
Describe ‘tumour doubling time’.
Time for a tumour to double in size
A reflection of the ‘growth fraction’
Tends to lengthen as the tumour grows
Do early or late tumours respond best to chemotherapy/radiation therapy?
Early ones! Tumour cells divide and grow rapidly
By the time they are detectable - growth fraction is reaching plateau, less susceptible to destruction than rapidly-dividing healthy cells
What does the grade of a tumour depend on?
Mitotic rate
Cellular and nuclear characteristics
What are some physical clues of local invasion by malignant tumours?
Diffuse, indistinct boundaries
Fixation of the tumour in one or more planes
Thickening of adjacent tissue
Spontaneous bleeding
How can a malignant tumour spread?
Via the blood, producing secondary tumours in any body organ
Via lymphatics, first to local and regional lymph nodes
Transcoelomic across the pleural or peritoneal space
Iatrogenic e.g. seeding by FNA or biopsy
What are paraneoplastic syndromes (PNS)?
Signs arising from the indirect effect of tumours’ production and release of biologically active substances
Affect distant organs and may be the first evidence of neoplastic disease
These effects may be life-threatening before cancer directly kills patient
What are some haematological paraneoplastic syndromes?
Anaemia - weakness, lethargy, tachypnoea
Thrombocytopenia - bleeding
Leukopenia - susceptibility to infection
Hyperviscosity syndrome
What are the two main causes of hyperviscosity syndrome?
Increased blood cell numbers with sludging blood and poor circulation - leukaemia, primary polycthaemia, secretion of excess erythropoietin causing secondary polycthaemia (EPO-secreting renal tumour/EPO-secreting leiomyoma) Excess gammaglobulins (especially IgM) secreted by multiple myeloma (plasma cell tumour)
What are the clinical signs of hyperviscosity syndrome?
Lethargy Tremors Thromboembolism Disorientation Episodic weakness Bleeding Ataxia Seizures Retinal haemorrhage and detachment
What are the local effects of PNS hyperhistaminaemia?
Oedematous swelling with erythema and pruritus
Tendency for localised bleeding due to heparin release
Delayed wound healing or dehiscence after surgery due to released proteases
What are the systemic effects of PNS hyperhistaminaemia?
Anaphylactic shock due to massive sudden release of histamine (vasodilation and hypotension) - premed with H1 antagonist (diphenhydramine) prior to surgical manipulation of tumour Gastroduodenal ulcer (can perforate) - treat with H2 antagonist (cimetidine/ranitidine) or proton pump inhibitor (omeprazole)
What immune-mediated PNS reactions might a patient show?
Immune-mediated haemolytic anaemia and/or thrombocytopenia (haematopoietic tumours)
Immune-mediated neuropathies (insulinoma)
Myasthenia Gravis - secondary to thymoma
Feline paraneoplastic alopecia (‘shiny skin disease’) (secondary to pancreatic and biliary carcinoma)
Pemphigus foliaceous (secondary to thymoma)
Describe PNS hypercalcaemia.
Most common PNS in dogs, relatively rare in cats
Tumours release a parathormone-like substance, called parathyroid hormone-related peptide (PTHrp)
Increases total and ionised calcium concentrations
Most commonly lymphoma
What are the clinical signs of PNS hypercalcaemia?
PUPD Anorexia Vomiting Lethargy, depression Muscular weakness Bradycardia
Describe PNS hypoglycaemia.
Pancreatic insulinoma - production of insulin
Excessive consumption of glucose - hepatoma, hepatocellular carcinoma, large intra-abdominal mass, chronic lymphocytic leukaemia
Release of an insulin-like factor - leiomyoma/GI stromal tumour (GIST)
Describe cancer cachexia.
Weight loss - muscle and fat loss
Abnormal metabolism - enhanced catabolism
Reduced food intake
What are the main aims of investigations into a tumour?
Make a histological/cytological diagnosis of type and grade
Determine extent of disease (stage) - local/distant spread
Investigate and treat any tumour-related/concurrent complications
How can we obtain a diagnosis of a tumour?
History Physical examination Laboratory testing Imaging Biopsy - cytology / histopathology
What should we do with all excised masses?
Submit for histology / fix and store in case owner changes their mind or the patient deteriorates
How can we collect cytology samples?
Touch/impression preparations
Fine needle aspirates (FNAs)
Analysis of body fluids/effusions
What can cytology samples tell us?
Nature of tumour, i.e. epithelial/mesenchymal/round cell
Cytological features
How can we collect a sample for histological exam?
Surgical/needle/punch biopsy
Surgical - incisional/excisional
What can a histological sample tell us?
Cellular features of malignancy
Tumour architecture
Invasion of adjacent tissues
Evidence of metastatic behaviour e.g. presence in blood vessels and/or lymphatics
How should we take a biopsy?
Procure a representative sample
Avoid superficial ulceration, inflammation or necrosis
Ensure adequate depth
Try to include a boundary between tumour and normal tissue
What are the aims of clinical staging?
Identify cytological or histological spread
Identify local invasion
Identify metastatic spread
Describe the TNM staging system.
T (0/1/2/3/4) = tumour, assessing size and invasiveness
N (0/1/2/3/4) = nodes, assessing local draining lymph nodes for evidence of spread
M (0/1/2) = metastasis, assessing spread to other organs