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Tumour

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Biology

Cancers are an example of how important regulation of cell division is as they arise due to uncontrolled mitosis. Cancer is a group of diseases caused by mutations of the genes that regulate mitosis and the cell cycle. When mitosis is unregulated, uncontrolled cell division occurs, and as a consequence, a group of abnormal cells called a tumour develops. Cancer is a common but potentially deadly disease. Despite this, if diagnosed early it is very much treatable.

Not all tumours are cancerous. Those that are cancerous are called malignant while those that are non-cancerous are called benign.

Tumour formation

Cancers start to form when genes that control cell division experience changes. This is called a mutation. Cell mutations are pretty common and are usually picked up and destroyed by regulatory functions such as early cell death or the body’s immune system. This doesn’t usually cause disturbance to the body as cells are constantly being replaced. When these cells are not destroyed, the harmful mutation is passed down to all its descendants. This means that many mutated and potentially cancerous cells are formed. This leads to a tumour.

Tumour: an irregular mass of cells.

Tumours Development StudySmarter

Figure 1. Cancer cells keep on reproducing to form a tumour. Source: Finty Royle - StudySmarter Originals.

Some tumours don’t spread from their original site and don’t cause cancer. Other tumours spread through the body and cause cancer.

Benign vs malignant tumours

The table below shows the different characteristics of benign and malignant tumours.

Table 1. Benign vs malignant tumours.

Benign

Malignant

Size

Can grow very large.

Can grow very large.

Rate of growth

Slow.

Fast.

Differentiation of cells

Highly differentiated/specialised.

Undifferentiated/ Unspecialised.

Removal

Usually removed by surgery alone.

Usually involves surgery, radiotherapy, and chemotherapy.

Locality

More localised effects on the body.

Often have systemic (whole-body) effects.

Damage

Less likely to be life-threatening. However, they can obstruct vital organs.

Much more likely to be life-threatening.

Metastasis

Produce adhesion molecules. These make the tumour cells stick together so they stay within the tissue they arise from. These are primary tumours.

Do not produce adhesion molecules so the tumour cells don’t stick together. They tend to spread to other regions of the body through the process known as metastasis. These are known as secondary tumours.

Capsule

They are surrounded by a capsule of dense tissue, so they remain a compact structure.

Do not have capsules surrounding them. Grow finger-like projections into other tissues.

Recurrence

Rarely recur after removal.

High rate of recurrence.

Malignant tumour: tumours that spread through the body and cause cancer.

Benign tumour: a mass of cells that doesn’t invade neighbouring tissue or metastasise.

Tumour appearance

As you can see in Figure 1, tumours have a different appearance from normal cells.

  • They have a larger and darker nucleus compared to other cells.

  • They may have more than one nucleus.

  • They have an irregular shape.

  • They don’t produce all proteins needed to function correctly.

  • They have different antigens on their surface compared to normal cells.

  • They don’t respond to the body’s regulating processes.

  • They divide by mitosis more frequently than normal cells.

Formation of a malignant tumour

How does a malignant tumour appear?

  • Malignant cells develop, divide, and invade normal tissues.

  • Some of the cells detach and spread through the blood and lymph vessels.

  • The malignant cells can squeeze through the capillary wall.

  • They then divide, producing a secondary tumour in a different location to the original tumour. This is called metastasis and it's very dangerous because these secondary tumours are hard to detect and remove.

Metastasis: a piece of a tumour cell breaks off and spreads to another part of the body.

Figure 2. Diagram showing how metastasis occurs. Source: smart.servier.com.

Factors that lead to cancer formation

There are several genetic factors that increase the likelihood of developing some cancers but there are also environmental factors. Chemicals and other agents that can cause cancer are called carcinogens. They damage the DNA and cause mutations.

Risk factors: factors that increase the likelihood of developing a disease.

Lifestyle factors that lead to increased risk of cancer include:

  • Alcohol intake.

  • Obesity and diet.

  • Smoking.

  • Exposure to UV light during either sunbathing or spending time outside.

  • Viruses spread during sexual intercourse.

There are also things that people may be exposed to at work:

  • Ionising radiation.

  • Chemical carcinogens.

Correlations

In your exams, you may be asked to evaluate evidence showing correlations between genetic and environmental factors and various forms of cancer.

A correlation is the statistical measure of the relationship between two variables. It is best demonstrated in variables with a linear relationship between each other and can be best visualised using a scatter diagram. When an increase in one variable is accompanied by the increase of another, we say that two variables a positively correlated. When one variable increases and the other variable decreases, we call it a negative correlation.

Bear in mind that just because there is a correlation between two variables, there isn’t necessarily causation. One variable may not cause changes in the other. Correlation assesses relationships between variables and these relationships may occur due to different factors.

Correlation coefficient

When sampling data from two variables we can use a calculation to determine whether the two variables correlate. The variables are plotted on scatter graphs which indicate possible relationships that we can test. Values will lie between 1 (perfect positive correlation) and -1 (perfect negative correlation).

This is the formula for the correlation coefficient:

x = the values of the first variable.

x̄ = the mean of the values of the first variable.

y = the values of the second variable.

ȳ =the mean of the values of the second variable.

Σ = the sum of.

(x - x̄) = the values of the first variable - the mean of the values of the first variable.

(y - ȳ) = the values of the second variable - the mean of the values of the second variable.

You can lay the data out in a table to work out the equation easily:

Then find the sum of each data column (except columns 3 and 4) and plug them into the equation.

Studies to measure correlation

To ensure correlations are statistically significant and not due to chance, scientists need large amounts of data that they can get using different methods.

Case studies

In case studies scientists compare a group of people who have the disease you want to study with a group of individuals who don’t have the disease.

People with disease = Cases

People without disease = Control

The scientists then collect information about risk factors that each group has been exposed to. The participants need to be matched by known risk factors such as gender and age. These factors aren’t investigated in the study but mean that the control group is representative of the case group.

Cohort studies

Cohort studies are very time-consuming and expensive in comparison to case studies. This is because it takes people a long time to develop diseases.

Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.

Disease prevention and treatment

Most types of medicine focus on treating an illness or injury. This means prescribing medicine or giving therapies that treat the illness and hopefully cure the patient. Preventive medicine aims to stop an illness before it starts. It takes a holistic approach by focusing on the many factors that play a role in health. This includes maintaining a healthy lifestyle.

When talking about cancer, we often use the term prevention. Cancer doesn’t have a single cause. Some of the causes are beyond our control (e.g. genetics, gender, or age) but some factors are within our control. These are called lifestyle factors. Lifestyle factors include:

  • Diet: there is strong evidence that suggests that a good diet rich in fruit, vegetables, and fiber reduces the risk of getting cancer.

  • Exercise: people who are more physically active are at a lower risk than those who do little or no exercise.

  • Sunlight: the more ultraviolet light someone is exposed to, the more at risk they are.

  • Smoking: both smokers and those who breathe in tobacco passively are at increased risk of cancer.

In a test, your teacher may ask you to evaluate experiments related to any one of these lifestyle factors. A common one is smoking, as there is a lot of evidence that shows that smoking increases the risk of lung cancer.

When tobacco was first introduced to Britain in the sixteenth century, it was seen as a harmful social activity. However, in the late 1940s, after an alarming increase in deaths from lung cancer, doctors began to wonder whether tobacco was the cause of this increase.

Some facts from NHS England include:

  • Smoking is one of the biggest causes of death and illness in the UK. Every year around 78,000 people in the UK die from smoking, with many more living with debilitating smoking-related illnesses.
  • Smoking increases your risk of developing more than 50 serious health conditions. Some may be fatal, and others can cause irreversible long-term damage to your health.
  • Over time, more and more studies have taken place and have caused the public to evaluate the risks associated with smoking. This changed view caused the government to take action by progressively raising taxes on tobacco, banning tobacco advertising, placing health warnings on tobacco products, and banning smoking in work and public places.

Tumour - Key takeaways

  • Tumours consist of an irregular mass of cells.
  • Some tumours don’t spread from their original site and do not cause cancer (benign). Other tumours spread through the body and cause cancer (malignant).
  • Metastasis occurs when a piece of tumour cell breaks off and spreads to another part of the body.
  • Environmental and genetic factors may cause cancer.
  • Preventive medicine aims to stop an illness before it starts and takes a holistic approach by focusing on the many factors that play a role in health. This includes maintaining a healthy lifestyle.

Tumour

A tumour develops due to abnormal cellular growth. In the case of cancer, this cellular growth is uncontrollable and spreads throughout the body.

Malignant and benign tumors.

During cancer the cell cycle is uncontrolled.

Through a process called metastasis.

They can affect a healthy cell’s genetic makeup as well as the body’s immune system. Specific viruses usually affect specific cells in the body, and therefore only certain viruses are linked with certain kinds of cancer.

The statistical measure of the relationship between two variables.

Final Tumour Quiz

Question

What is the general appearance of a tumour cell?

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Answer

  • They have a larger and darker nucleus compared to other cells. 

  • They may have more than one nucleus.

  • They have an irregular shape.

  • They don't produce all proteins needed to function correctly

  • They have different antigens on their surface compared to normal cells.

  • They don't respond to the body's regulating processes.

  • They divide by mitosis more frequently than normal cells.

Show question

Question

Metastasis definition

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Answer

When a piece of tumour cell breaks off and spreads to another part of the body.

Show question

Question

What are cohort studies?

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Answer

Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.

Show question

Question

What factors affect the risk of developing cancer?

Show answer

Answer

  • Diet - There is strong evidence that suggests that a good diet rich in fruit, veg and fibre reduces the risk of getting cancer.
  • Obesity - Linked to diet, being overweight also increases the risk of cancer. 
  • Exercise - People who are more physically active are at a lower risk than those who do little or no exercise.
  • Sunlight - The more ultraviolet light someone is exposed to, the more at risk they are.
  • Smoking - Both smokers and those who breathe in tobacco passively are at increased risk of cancer.

Show question

Question

Correlation definition

Show answer

Answer

A correlation is the statistical measure of the relationship between two variables. It is best demonstrated in variables with a linear relationship between each other.

Show question

Question

What are cohort studies?


Show answer

Answer

Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.

Show question

Question

Benign definition

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Answer

A mass of cells that doesn’t invade neighbouring tissue or metastasise

Show question

Question

How does a malignant tumour form?

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Answer

  • Malignant cells develop, divide and invade normal tissues.

  • Some of the cells detach and spread through the blood and lymph vessels.

  • The malignant cells can squeeze through the capillary wall.

  • They then divide, producing a secondary tumour in a different location to the original tumour.

Show question

Question

What is a disadvantage of cohort studies?


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Answer

Cohort studies are very time consuming and expensive in comparison to case studies. This is because it takes people a long time to develop diseases.

Show question

Question

Malignant definition


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Answer

Tumours that spread through the body and cause cancer.

Show question

Question

What causes cancers to arise?


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Answer

Uncontrolled cell division

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Question

How are mutations kept under control?


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Answer

  1. Picked up by various regulatory functions in the cell cycle
  2. Early cell death (apoptosis)
  3. Being destroyed by the bodies immune system

Show question

Question

What are cohort studies?


Show answer

Answer

Cohort studies follow a group over time to see who develops diseases and who doesn't. Exposures to risk factors are recorded over time.

Show question

Question

Compare and contrast benign and malignant tumours.


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Answer

Both benign and malignant tumours can grow large however benign tumours grow slowly, and have more localised effects whereas malignant tumours grow rapidly and have systemic effects. Benign tumours can usually be removed by surgery alone whereas malignant tumours often require radiotherapy or chemotherapy as well. They are also more likely to be life-threatening than benign tumours and have a high rate of recurrence. Benign tumours are often surrounded by a capsule and don't metastasise whereas malignant tumours don't have a capsule and do metastasise.

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Question

What is the correlation coefficient used for?


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Answer

To determine whether too variables correlate. 

Show question

Question

What are case studies?

Show answer

Answer

A group of people who have the disease to be studied are compared with a group of individuals who do not have the disease.

Show question

Question

What is the aim of preventative medicine?

Show answer

Answer

To stop an illness before it starts and takes a holistic approach by focusing on the many factors that play a role in health. This includes maintaining a healthy lifestyle.

Show question

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