Characteristics of Tumours Flashcards
What is the definition of tumour?
a swelling or mass of any kind
(it is not specific to cancer or neoplastic processes - the swelling in inflammation is referred to as ‘tumour’)
What is the definition of neoplasia?
new, uncontrolled growth of cells that is not under physiological control
it can be benign or malignant
What is the definition of cancer?
a generic term for a large group of diseases characterised by the growth of abnormal cells beyond their usual boundaries that can then invade** adjoining parts of the body and/or **spread to other organs
this is a malignant neoplasia
What are the 8 hallmarks of cancer?
- sustaining proliferative signalling
- evading growth suppressors
- avoiding immune destruction
- enabling replicative immortality
- activating invasion and metastasis
- inducing angiogenesis
- resisting cell death
- deregulating cellular energetics
How are cancer cells able to replicate infinitely without dying?
Normal cells have telomeres
The length of the telomere determines how many times the cell can divide before it dies
Cancer cells keep their telomeres long forever so that they can continue dividing
What is meant by ‘inducing angiogenesis’?
cancer cells can form new blood vessels so that they have a constant supply of oxygen and nutrients
What is meant by ‘deregulating cellular energetics’?
cancer cells are able to switch around metabolism in the body to maximise the amount of energy they receive compared to waht is available
What are the 2 reasons why mutations that lead to cancefr may occur?
- environmental factors can cause mutations
- inherited genetic mutations
How does a mutation turn a cell cancerous?
each mutation helps the cell to acquire one of the hallmarks of cancer
the mutations accumulate until the cell becomes malignant
What are 3 common mutated genes involved in cancer syndromes?
p53, BRCA1 and retinoblastoma
these are tumour suppressor genes
a mutation in any of these genes can contribute to cancer
What is the definition of embryological histogenesis?
the formation of differentiated tissues from undifferentiated endoderm, ectoderm and mesoderm cells
What types of cell are typically formed from endoderm?
- lung cells (alveolar cells)
- thyroid cells
- digestive cells (pancreatic cells)
What types of cell are typically formed from mesoderm?
- cardiac muscle cells
- skeletal muscle cells
- tubule cells of the kidney
- red blood cells
- smooth muscle cells in the gut
What types of cells are typically formed from ectoderm?
- skin cells of epidermis
- neurone on brain
- pigment cells
What is meant by tumour histogenesis?
tumours are named according to the tissues from which they arise
Where do carcinomas, sarcomas and melanomas arise from?
carcinoma:
arises from epithelial lining of the digestive tract
sarcoma:
arises from smooth muscle cells
melanoma:
arises from pigment cells
What is the definition of ‘differentiation’?
the extent to which a neoplasm resembles its tissue of origin
In terms of differentiation, what are the 3 ways in which a neoplasm could be described?
well-differentiated:
neoplasm closely resembles tissue of origin
moderately-differentiated:
neoplasm shows some resemblance to tissue of origin
poorly-differentiated:
neoplasm does NOT resemble tissue of origin
How well differentiated are the following images?
What is significant about a well-differentiated tumour?
the more well-differentiated tumour makes a lot of keratin
well-differentiated tumours tend to be less aggressive
What is the definition of anaplasia?
a neoplasm that is poorly differentiated and highly pleomorphic
What is meant by pleomorphic?
What is significant about an anaplastic tumour?
pleomorphic describes variation in cell size and shape
an anaplastic tumour is very aggressive and spreads rapidly
there are no clues as to which tissue it has come from as it is so poorly differentiated
What is one of the most common anaplastic tumours?
What is the main risk associated with this?
anaplastic thyroid carcinoma
it compresses the airway and leads to problems with breathing
What type of tumour is this?
anaplastic
What cancers in the UK have the highest female incidence?
breast, lung and bowel
What types of skin cancers are shown?
basal cell and squamous cell carcinomas are non-melanoma skin cancers
Why are non-melanoma skin cancers excluded from cancer statistics even though they are common?
they represent <1% of cancer deaths
even though they are very common, very rarely does anyone die from them
What cancers had the highest female mortality in the UK?
lung, breast and bowel
lung cancers cause more deaths as they tend to be more aggressive and have a poorer prognosis
Which cancers have the highest male incidence in the UK?
- prostate
- lung
- bowel
What cancers have the highest male mortality in the UK?
lung, prostate and bowel
Why is liver cancer the most common cancer in parts of Africa?
due to an increased incidence of hepatitis virus
aflatoxins made by a fungus can invade crops, reach the liver and contribute to cancer
Why is Kaposi sarcoma the most common cancer in some parts of africa?
due to an increased incidence in HIV
Why is lip/oral cancer the most common cancer in parts of Asia?
due to chewing tobacco and the betel nut, which contains carcinogens
Why is cervical cancer the most common cancer amongst females in some countries?
this is associated with an increased incidence of HIV
HIV lowers the immune system, meaning that the body is less able to clear the HPV virus
Being unable to clear the virus increases risk of developing cervical cancer
What are the top 5 cancers in women with the highest mortality?
How is this measured?
- pancreas
- liver
- mesothelioma
- lung
- oesophagus
it is measured as predicted five year survival rate (%) for women diagnosed today
What are the top 5 cancers in men with the highest % mortality?
- pancreas
- mesothelioma
- lung
- liver
- oesophagus
How do benign and malignant tumours vary in their ability to invade?
benign:
neoplasm does NOT invade surrounding tissues
malignant:
neoplasm DOES invade surrounding tissues
How do benign and maligant tumours vary in their ability to metastasise?
benign:
do not metastasise
malignant:
not all malignant tumours metastasise, but they all have the capacity to
they metastasise by 3 methods:
- lymphatic
- haematogenous
- direct seeding
How do malignant tumours metastasise lymphatically?
they invade into the lymphatic vessels which drain into the lymph nodes
How do malignant tumours metastasise by haematogenous means?
this is spreading via the blood
the next capillary bed through which blood flows is where the tumour will spread to
How do malignant tumours metastasise through direct seeding?
this occurs when the tumour grows beyond the boundaries of the organ it is in and into a body cavity
How do the rates of growth differ in benign and maligant tumours?
benign:
slow rate of growth
malignant:
fast rate of growth as cell division exceeds cell death
How does the extent of differentiation vary in benign and malignant tumours?
benign:
usually well differentiated
malignant:
can be anything from well to moderate to poorly differentiated or anaplastic
How does the prognosis of benign and malignant tumours vary?
benign:
these are rarely fatal unless in the intercranial cavity
the tumour may grow and compress the brain
malignant:
these are often fatal
Why are some benign tumours removed and others are not?
some benign tumours can undergo changes and become malignant
tumours in different locations have different capacities at doing this
What are the 3 categories of tumour complications?
- effects of the primary tumour
- effects of the distant metastases
- paraneoplastic syndromes
What complication due to an effect of a primary tumour is shown here?
a tumour can invade into and replace normal tissues/organs
this leads to failure of that organ to function
the liver and bone marrow are most commonly implicated
How can primary tumours cause complications through pressure?
Which area is particularly vulnerable to this?
pressure on normal tissues from the tumour can lead to a failure of that organ to function
this is usually within the intercranial cavity
pressure on the brain causes it to stop functioning
How can an effect of the primary tumour affect local blood vessels?
the tumour can invade into blood vessels and cause bleeding
the tumour can put pressure on blood vessels and compress them, leading to ischaemia as any structure distal to the compression is not receiving oxygen
How can an effect of a primary tumour involve nerves?
pressure or invasion into nerves leads to loss of nerve function and pain
What happens if a primary tumour grows into a lumen?
this leads to obstruction
e.g. pancreatic cancers can block the bile duct, leading to the pateitn developing jaundice
What is meant by a fumigating tumour?
a tumour that can ulcerate through the skin
this is prone to infection and bleeding
this is an effect of a primary tumour
What is meant by ‘effects of distant metastases’?
when a cancer spreads to different parts of the body, forming new (secondary) tumours
What types of tumour complications are caused by the effects of distant metastases?
all the same complications that can be caused by a primary tumour, but in the site at which the tumour has spread to
What is meant by a paraneoplastic syndrome?
signs and symptoms that are NOT related to the local effects of the primary or metastatic tumours
Why do paraneoplastic syndromes develop?
they develop as a result of either:
- proteins/hormones secreted by tumour cells
- immune cross reactivity between tumour cells and normal tissues
What is cachexia?
What causes it?
cachexia is wasting away through loss of muscle and fat mass
this is due to a tumour changing the metabolism of the body so that the tumour cells consume all the energy available
this is a paraneoplastic syndrome
How may Cushing’s syndrome develop as a paraneoplastic syndrome?
if a tumour secretes ACTH or cortisol
What happens in Lambert Eaton Myasthenic Syndrome?
How is it an example of a paraneoplastic syndrome?
- proteins made by tumour cells are mutating and forming new proteins that the body does not recognise
- the abnormal protein may look like something in the CNS
- the body recognises the abnormal protein and makes antibodies against it
- as the protein looks similar, the body accidentally attacks the CNS and causes symptoms in the brain
This is immune cross-reactivity
What is the definition of stroma?
cells that support the parenchyma
What is the parenchyma?
ORGAN = PARENCHYMA + STROMA
cells that perform the actual function of an organ
e.g. pneumocytes in the lungs that perform gas exchange
What is shown by the green lines?
parenchyma in the bowel
these cells are producing mucin and absorbing fluid from stool
What is shown by the orange lines?
stroma
these are all the other cells in between the parenchyma
What are the 3 main cell types contained within the stroma?
blood vessels:
these supply oxygen and nutrients
fibroblasts (& collagen they make):
these act as a support structure
immune cells:
these prevent infection and repair tissue damage
What is shown by the blue line?
tumour
What is shown by the orange line?
tumour stroma
this is also known as desmoplastic stroma
What cells are found in tumour stroma?
tumour stroma is composed of the same cells as normal stroma, but the stromal cells have different fuctions
What is the role of tumour stroma?
stromal cells help the cancer cell acheive the 8 hallmarks of cancer
they help the cell do everything it needs to become malignant
What is meant by transcoelomic spread of tumour cells?
spread of tumour cells through the body wall into the abdominal and chest cavities
