Lect 18 - Characteristics of Tumours Flashcards
what is the WHO definition of cancer?
“Cancer is the uncontrolled growth of cells, which can
invade and spread to distant sites of the body”
tumour is synonymous with what term in modern medicine?
neoplasm
what is HISTOGENESIS
The differentiation of cells into specialised tissues and organs during growth from undifferentiated cells (the 3 primary germ layers)
what is the incidence of cancer (2011)
331,487 cases - 161,823 deaths
describe the general trend in cancer incidence and mortality
incidence slowly going up. mortality very slowly going down
which cancers are the most common?
most common:
breast 26% (of women)
lung ~ 15%
colon and rectum 10%
prostate 25% (of men)
note these cancers are also the most fatal ie kills the most people (lung is the worst). this is obviously skewed by how many of them there are.
what 4 factors are used to categorise tumours?
Differentiation
Rate of Growth
Local Invasion
Metastasis
do Malignant tumours tend to grow more rapidly than benign tumours?
Many exceptions to this rule
Not useful to discriminate
Different malignancies show varied growth rates
what is the definition of Differentiation
The extent that neoplastic cells resemble the corresponding normal parenchymal cells, morphologically and functionally
WARNING - Well-differentiated malignant tumours and benign tumours can look very similar
are benign or malignant tumours more likely to be poorly differentiated?
Benign tumours
usually well-differentiated
Mitoses are rare
Malignant neoplasms
wide-range of parenchymal differentiation
Most exhibit morphologic alterations showing malignant nature
what is Anaplasia?
Neoplasms comprised of very poorly-differentiated cells are described as anaplastic - Cannot be identified by morphology alone
“Telltale sign of malignancy”
what Morphological Changes can be seen with tumours which are not well differentiated?
Pleomorphism Abnormal nuclear morphology Mitoses Loss of polarity Other changes
what is Pleomorphism?
Variation in:
Size
shape
of cells and or their nuclei
how do you measure if cells are showing Pleomorphism?
Nuclear to cytoplasmic ratio Variability in nuclear shapes (faces) Chromatin distribution Hyperchromatism (dark) Abnormally large nucleoli
what variations in mitosis suggest malignancy?
atypical mitotic figures such as:
Tripolar
Quadripolar
Multipolar spindles
what does loss of polarity mean?
The orientation of cells is disturbed. Therefore there is disorganised growth
what measure is based on a cancer’s level of differentiation?
GRADE
Well differentiated = low grade / grade 1
Moderately differentiated = intermediate / grade 2
Poorly differentiated = high grade / grade 3
why is it important to have well differentiated tumours?
Better differentiation = better retention of normal function
Benign and well-differentiated carcinomas frequently secrete hormones characteristic of origin (can help diagnosis)
what is a Paraneoplastic Syndrome
a set of symptoms caused by a cancer - often because of hormones
what types of cancer have the ability to invade tissues?
malignancies.
what stops a benign tumour from invading tissues?
A rim of compressed fibrous tissue is formed. ENCAPSULATION.
extracellular matrix is deposited by stromal cells activated by hypoxia from pressure of tumour.
what is Pseudoencapsulation?
the attempt by the body to encapsulate a malignant tumour. Microscopically seen as rows of cells penetrating margin.
what is Metastasis?
“Spread of a tumour to sites physically discontinuous with the primary tumour”
Reduces life expectancy significantly
30% of non-skin malignancies at diagnosis have metastasised
what pathways of Metastasis are there?
Direct seeding
Lymphatic spread
Haematogenous spread
what is Direct Seeding?
Neoplasm penetrates a natural open field without physical barriers
Eg peritoneal cavity, pleural, pericardial, subarachnoid, joint spaces
what is Lymphatic Spread?
spread via lymphatic system.
most common pathway - particularly important if there are lymphatic vessels at the tumour margins.
what are sentinel nodes?
The first node in a regional lymphatic basin that receives lymph flow from the primary tumour
Identified by:
Injection of radiolabelled tracers/coloured dyes
what is Haematogenous Spread
tumours spreading via bloodstream.
Typical of sarcomas
Also seen in carcinomas!
Veins more easily penetrated as they have Thinner walls
where do cells moving via Haematogenous Spread tend to go?
Often come to rest in first encountered capillary bed
Liver (portal) and lungs (caval) most frequently involved
what is stroma?
connective tissue framework that neoplastic cells are embedded in
what is a Desmoplastic reaction?
fibrous stroma formation due to induction of connective tissue fibroblast proliferation by growth factors from the tumour cells
what does the stroma contain?
Cancer-associated fibroblasts
Myofibroblasts
Blood vessels
Lymphocytic infiltrate
give some local Clinical Complications of Tumours.
Compression/Destruction
give some metabolic effects of tumours.
Warburg Effect
(Produces energy by high rate of glycolysis with fermentation of lactic acid)
Cachexia
(profound weight-loss despite apparently adequate nutrition)
Neuropathies
Myopathies
Venous thrombosis
