Neoplasia Flashcards
(168 cards)
1
Q
Describe a neoplastic tumour.
A
A focal, purposeless overgrowth of one cellular component.
2
Q
Some tumours are driven by normal genes which are expressed inappropriately. What are they?
A
Oncogenes
proto-oncogenes in a normal cell
3
Q
Some tumours are triggered by the loss of normal genes. What are they?
A
Tumour suppressor genes
4
Q
What is dysplasia?
A
Disordered tissue organisation which can be pre-neoplastic.
Change is reversible, cells have altered differentiation.
5
Q
What is neoplasia?
A
A new growth which persists after the initial stimulus is removed.
6
Q
What is a carcinoma?
A
A malignant epithelial tumour
7
Q
What is carcinogenesis?
A
Production of cancer
8
Q
What is a blastoma?
A
Poorly differentiated cell of embryonic type, tend to be very aggressive.
Mainly seen in children.
9
Q
What is a benign tumour that arises from a gland called?
A
Adenoma
10
Q
What is a benign tumour which arises from a gland and contains cavities?
A
Cystadenoma
11
Q
What is a club-shaped tumour dangling from a surface?
A
Polyp
12
Q
What is a sessile polyp?
A
A polyp which lacks a stalk
13
Q
What is an adenomatous polyp?
A
A polyp which contains glandular growth.
14
Q
What is a papilloma?
A
An outgrowth from an epithelial surface with long, thin branches.
15
Q
What is a malignant tumour that arises from a gland?
A
Adenocarcinoma
16
Q
What is a benign tumour arising from fibroblasts?
A
Fibroma
17
Q
What is a benign tumour arising from bone?
A
Osteoma
18
Q
What is a benign tumour arising from fat cells?
A
Lipoma
19
Q
What is a benign tumour arising from cartilage?
A
Chondroma
20
Q
What is a benign tumour arising from blood vessels?
A
Haemangioma
21
Q
What is a benign tumour arising from lymphatic vessels?
A
Lymphangioma
22
Q
What is a malignant tumour arising from bone marrow?
A
Myeloma
23
Q
Are lymphomas benign or malignant?
A
Malignant
24
Q
What is a benign tumour arising from smooth muscle?
A
Leiomyoma
25
What is a malignant tumour arising from smooth muscle?
Leiomyosarcoma
26
What is a malignant tumour arising from striated muscle?
Rhabdomyosarcoma
27
What is a benign tumour arising from striated muscle?
Rhabdomyoma
28
What is a tumour of neurons?
Ganglioneuroma
29
What is a malignant glial tumour?
Glioblastoma
30
What is a pleomorphic adenoma of salivary glands?
Benign tumour in the salivary glands which contains mixtures of epithelium, connective tissue and cartilage.
31
What is a fibroadenoma of the breast?
A benign tumour in the breast which contains glands and connective tissue
32
Why can teratomas contain material that is found anywhere in the body?
They are derived from cells which are so primitive (germ line cells) that they can produce all three embryonic leaflets.
33
What is a hamartoma?
A lump of tissue belonging to the organ in which it is found but has been wrongly assembled in the course of development.
Are present at birth and grow with the person.
34
What is a choristoma?
Ectopic tissue.
| Lumps of normal tissue which doesn't belong in the organ where the lump is found.
35
What properties do tumour cells share with embryonic and foetal cells?
They tend to grow quickly and are immature
36
What is anaplasia?
Cells which don't have the morphological characteristics of a normal cell.
37
What is tumour progression?
Tumours becoming gradually more poorly differentiated in their life.
38
What are the features of a rapidly dividing cell seen microscopically?
More cytoplasmic basophilia due to increased RNA
Nucleoli increased in size and number
Mitoses increased and mitotic figures may be abnormal
39
How can mitotic figures be a measure of malignancy?
The number is proportional to the rate of growth and therefore aggressiveness of the tumour.
40
What is atypia?
Structural abnormality. Tends to parallel the degree of aggressiveness.
Size and shape of the cell is abnormal, nucleus is large and the secretions become irregular.
41
What are the behavioural changes in malignant cells?
Immortality
Loss of anchorage dependency
Loss of contact inhibition
Decreased requirement for growth factors as they supply their own
42
What are the functional changes in malignant cells?
Mobility - allows invasion and gives them the potential to move to another site.
Decreased adhesion between cells which plays a role in invasion
Tendency to shed surface molecules.
- Collagenase helps the cells invade through the ECM
- Tissue factor may lead to exaggerated clotting.
43
How can surface-related changes to malignant cells assist in diagnosis or treatment of a cancer?
Some of the surface molecules which are shed can be found in the blood and are known as tumour markers.
They are useful for diagnosing a particular malignancy or monitoring response to a treatment.
44
How and where do ulcerated tumours tend to develop?
Tend to arise from a bacterially contaminated surface such as the skin.
In the gut this is thought to be secondary to bacterial infection and digestive enzymes. The surface of the tumour is eroded by friction, then colonised by bacteria which causes a non-healing ulcer.
An ulcer with a raised edge strongly suggests an ulcerated tumour rather than a non-neoplastic ulcer.
45
What is scirrhous carcinomas?
A tumour with lots of connective tissue stroma. They are firm or hard.
46
Describe the cut surface of most tumours.
Most are white
Foci of necrosis common in malignant tumours
Large spaces filled with cysts suggest the tumour is epithelial.
47
What do you look at to find where a tumour has arisen from?
Identifying features for a specific cell type
| If the tumour has lost all differentiation they can still be recognised by a specific antibodies.
48
What do you look at to determine how aggressive a tumour is?
Cellular abnormalities - lack of differentiation, cytologic atypia, pleomorphism
Architectural atypia - abnormal cellular pattern, infiltration
49
What are the secondary changes that can be seen in a tumour?
Ulceration
Necrosis (seen in the centre of tumours, more common in malignancy)
Calcification (seen in dead cells/necrotic masses)
Tortion (seen in pedunculated tumours, results in red infarct)
50
Give an example of a cell other than a tumour cell which is able to invade tissues.
Trophoblasts - invade the uterine wall
| Leukocytes - invade tissues in inflammation
51
What is a metastasis?
A secondary tumour which has arisen from detached, transported cells.
52
Through what channels are metastases able to travel to a new site?
Blood
Lymph
Fluid in tissue spaces
53
Are metastases able to metastasise?
Yes
54
Why are metastases the most lethal expression of malignancies?
Greatly increase the disease burden
55
What are microscopic metastases and which cancers are most likely to produce them before excision?
Non-clinical, dormant metastases.
Breast cancer/malignant melanoma
56
Which vessels do metastases most commonly permeate?
Capillaries or veins (have very thin walls)
57
Which cancer is most likely to invade a large vein and grow through it?
Renal cell carcinoma
58
Where do tumours in organs which are drained by the portal system metastasise to?
Liver
59
What is the seed and soil model for tumours which metastasise?
The 'seed' is the tumour type, and the 'soil' is the tissue in which it embeds. Certain types of tumour have a preferential 'soil', yet the reason for this is yet unknown.
60
Where do breast carcinomas tend to metastasise to?
Lymphatics
| Skeleton
61
Where do bronchial carcinomas tend to metastasise to?
Adrenal glands
62
What are Kruckenburg tumours?
Bilateral mesenteric tumours of the ovaries
63
Why are the lungs a common site for the metastases of many tumours?
They are the first large capillary bed after entry into the veins.
64
What is a common location for carcinomas to metastasise to, but is very rare for sarcomas?
Lymphatics
| exception: rhabdomyosarcomas
65
Describe peau d'orange and why it occurs.
Carcinomas of the breast permeate the lymphatics of the overylying skin, causing the skin to become oedematous and puckered.
66
If lymph nodes near a tumour are swollen, what could be the cause if it has not metastasised?
Secondary to antigens and irritants which leach out of a tumour (especially if necrotic, ulcerated or infected).
Draining lymph nodes can then undergo hyperplasia.
67
How can seeding of a metastasis into the peritoneum cause ascites?
Fluid accumulation secondary to factors produced by tumours which cause leaking of fluid from the peritoneal membrane
OR
Secondary to fluid leaking from the surface of the tumour
68
Why is implantation of metastases onto epithelial surfaces rare?
They are inhospitable surfaces - covered with mucus, cornified cells and bacteria.
69
How does basal cell carcinoma present?
Small, crusty lesions which don't heal and appear on areas frequently exposed to the sun.
70
How does basal cell carcinoma most commonly cause death?
By extensive invasion of the surrounding tissue
| does not tend to metastasise
71
Why do tumours of the CNS rarely metastasise to the body?
In an enclosed space and often kill before visceral metastases are found.
72
Give the steps required for a cell to produce haematogenous metastases?
Separate itself from tumour mass and move in the right direction
Digest through intercellular matrix and vascular basement membrane to enter the lumen of a vessel
Escape defensive systems in the blood
Survive impact and mechanical squeeze in small vessels
Penetrate the endothelium and basement membrane, escape further dangerous cells
Multiply, induce angiogenesis and establish a tumour.
73
State 2 things in the blood which are part of the body's defense against tumours.
```
Antibodies
Complement
Macrophages
Natural killer cells
Toxic concentrations of oxygen
Blood clotting
```
74
What connects malignant cells to each other?
E-cadherin
75
What connects malignant cells to stromal proteins in the basement membrane?
Integrin
76
Give an example of an enzyme produced by malignant cells to help them digest through connective tissue.
```
Collagenase
Matrix metalloproteinases (MMP)
```
77
Are tumour cells more likely to penetrate vessels of the tumour itself or preformed vessels?
The tumours own vessels because they are defective (may lack a basement membrane or endothelial lining).
78
What connects malignant cells to the basement membrane in blood vessels?
Laminin receptors
79
Give an example of how a tumour causing compression can be hazardous or cause problems even if it is not cancerous.
Bulky lesions in the brain cause damage structures and cause ischaemia
They can also cause herniation of the brain into foramen magnum, causing compression of vital structures and potentially death.
Compression of the optic nerve can cause blindness
Compression of the great veins can cause the face to swell.
80
What problems can be caused by ulceration on the surface of a tumour?
Bleeding and/or infection
| Perforation
81
What is paraneoplastic syndrome?
Symptom complexes which accompany tumours and concern distant targets whether the mechanisms be hormonal, toxic, immunologic or unknown.
82
Give something which can cause paraneoplastic hypercalcaemia/
Parathyroid tumour
Extensive metastatic bone destruction (seen in multiple myeloma)
Parathyroid hormone-like peptide production
Squamous cell carcinoma producing PTC
83
What are the symptoms of carcinoid syndrome?
Flushed, sweating, diarrhoea, tachycardia, anxiety
84
What are the most common substances for carcinoid tumours to secrete?
5-HT and kalikrein
85
What hormone do renal cell carcinomas commonly produce and what problems does this cause?
Erythropoietin
Causes high haematocrit causing symptoms related to high blood viscosity
(e.g. spontaneous bleeding from mucous membranes,retinopathy, neurological symptoms)
86
Describe why tumours can induce a hypercoagulative state.
Platelets can be activated by tumour products e.g. ADP
| Tumours secrete procoagulants e.g. tissue factor/mucins
87
Describe migratory thrombophlebitis (Trousseau's syndrome)
Bouts of inflammation or swelling of the leg veins caused by blood clots, found in multiple locations without an apparent predisposing factor.
Often due to underlying cancer.
Frequently seen in pancreatic, lung or stomach cancer.
88
Describe acanthosis nigricans
Symmetric, brown, warty hyperpigmentation with hyperkeratosis of the axilla and other flexural areas.
Majority occur in association with an internal malignancy, especially carcinoma of the gastrointestinal tract.
89
Give two consequences of metastasis which are miscellaneous
```
Myositis
Abnormal pigmentation
Finger clubbing
Pruritis
Immunosuppression
Neuropathy (cerebellar degeneration/glove and stocking neuropathy)
```
90
What is cachexia?
Wasting of the whole body
91
What is cachexia thought to be caused by when associated with cancer?
Induction of macrophages to produce TNF which causes wasting
Loss of appetite and changes in sense of taste
Host metabolism is increased
92
What is tumour lysis syndrome?
Extensive acute necrosis of a tumour which is very sensitive to x-rays or chemotherapy.
Can be life threatening by releasing toxic amounts of potassium and uric acid
93
What tumour commonly causes tumour lysis syndrome?
Burkitt's lymphoma
94
Give two methods with which a cancer can cause death.
```
Infection (cancer and its treatments are anti-inflammatory)
Haemorrhage and thromboembolic phenomena
Cachexia
Respiratory failure
Renal failure
```
95
What is an astrocytoma?
A primary CNS tumour which is mainly found in the cerebellum in children and the cerebral hemispheres in adults.
96
What is a melanoma?
A (usually) malignant tumour of melanocytic origin, mostly found in the skin but primary lesions can also be seen in the CNS, GI, GU tract, inner ear
Is curable if excised before it begins to invade the dermis.
97
What is a carcinoid tumour?
An endocrine tumour of the gut and respiratory tract which doesn't produce a known peptide hormone or produces a mixture of peptide hormones.
Often metastasises to the lymph nodes.
98
What is the most common carcinoma of the exocrine pancreas?
Ductal adenocarcinoma
99
What are the symptoms of pancreatic carcinoma?
Weight loss
Obstructive jaundice
Flitting venous thrombosis (Trousseau's sign)
100
Explain why lung carcinomas tend to have a poor overall prognosis.
Patient age
Comorbidities are common
Late presentation with advanced dissemination at the time of diagnosis
101
What is squamous cell carcinoma of the skin?
Malignant skin neoplasm associated with chronic sun exposure and is locally invasive. Metastasises late.
102
What is basal cell carcinoma?
A very common skin malignancy related to chronic sun exposure which occurs most commonly on the face. Is locally very invasive but metastases are rare.
Are ulcerated irregular lesions with a raised pearly border, often with tiny blood vessels visible on the border
103
What is gastric carcinoma?
Majority are adenocarcinomas, many arise from a background of chronic gastritis and intestinal metaplasia. Generally present when clinically advanced.
Early cases have a good prognosis.
104
What is the difference between intrinsic and extrinsic factors in neoplasia pathogenesis?
Intrinsic - genes/hormones. Things which are in the body from birth or as a result of body processes.
Extrinsic - chemicals/radiation. Things which our bodies are exposed to that increase the risk of neoplasia.
105
What did studies into 2-napthylamine as a carcinogen show about the relationship between exposure and malignancy?
Long delay between carcinogen exposure and onset of malignancy.
Risk depends on total dosage
Sometimes has organ specificity.
106
Describe the feature of carcinogenic molecules which allows them to cause damage.
Are electrophilic reactants.
Have a relatively electron-deficient site which makes them seek nucleophilic sites. They then form covalent bonds.
Nucleophilic groups are relatively abundant as DNA, RNA and proteins.
107
Give an example of a mutagenic chemical carcinogen.
```
Polycyclic aromatic hydrocarbon
Aromatic amines
N-nitroso compounds
Alkylating agents
Diverse natural products e.g. aflatoxin
```
108
What are procarcinogens?
Inactive carcinogens which need to be converted to carcinogens, e.g. by the cytochrome P450 enzymes in the liver.
109
How do immigrant studies give evidence for diet having a role in carcinogenesis?
People who emigrate and change their diet will change their risk of certain cancers depending on the country that they move to.
110
Give a piece of evidence for diet having a role in carcinogenesis which is unrelated to immigration.
Incidence of cancer along the colon and rectum increases in the direction of faecal progress, which suggests a role for contact time between mucosa and faeces.
111
Nitrosamine is a dietary carcinogen. What cancer is it specifically linked to and where can it be found?
Gastric cancer
| Present in tobacco smoke and food additives.
112
What produces aflatoxin B1, and what cancer is it associated with?
Aspergillus flavus
| Liver cancer
113
What agents present in the diet can inhibit mutations and tumour formation?
Fibre
Vitamin A
Vitamin C
114
What tumour locations correlate with hormonal levels?
Breast
Ovary
Endometrium
Prostate
115
How can obesity be linked to endometrial cancer?
Adipose tissue converts androgens to oestrogens which increases the risk of endometrial cancer.
116
Give an example of an occupational carcinogen and the problems that it can cause.
Asbestos.
| Inhaled fibres causes fibrosis and malignant tumours of mesothelium of the pleura, pericardium and peritoneum.
117
Give an example of a therapeutic carcinogen.
Radiotherapy (targets DNA, but not specific to tumour cells)
Diethylstilboesterol (stops bleeding in pregnancy, causes adenocarcinoma of the vagina in female daughters of the treated woman)
Immunosuppression
118
Describe how UV light can be a carcinogen, and indicate a cancer that it is related to.
Behaves as a complete carcinogen, completed exposures are needed. Damage DNA strands by forming dimers and cross-links.
Basal cell carcinoma/squamous cell carcinoma/malignant melanoma
119
Describe how ionising radiation can be a carcinogen and give an area which is especially sensitive to it.
Single exposure is enough.
Strips electrons from atoms, causing damage directly or causing free radicals. Injury can shorten cell survival.
Bone marrow/intestinal epithelia because they have high mitotic rates.
120
What are the gene products of proto-oncogenes?
Growth factors
Growth factor receptors
Links an intracellular network so external stimuli induce cell proliferation
121
What are the two ways that a protooncogene can be converted to an oncogene.
Encode a hyperactive protein
| Encode too much protein
122
Give an example of a DNA oncogenic virus and a neoplasm that it causes.
Hepatitis B - hepatocellular carcinoma
Human papilloma virus - papilloma/cervical carcinoma
Epstein Barr virus - Burkitt's lymphoma/nasopharygeal carcinoma
Molluscum contagiosum - benign molluscum bodies
123
Give an example of an RNA oncogenic virus and describe how it increases the risk of cancer.
Human T-cell lymphotrophic virus-1 - Relative of HIV which affects helper T-lymphocytes
Humman immunodeficiency virus - tumours are related to immunosuppression e.g. Kaposi's sarcoma.
124
State a parasite which can cause cancer and give an example of this.
Heliobacter pylori - strong association with stomach cancer
Schistosoma haematobium - associated with squamous cell carcinoma of the bladder
125
What is the function of RAS in normal cells, and how is it changed in neoplasms?
Encodes a small G-protein which relays signals into the cell to push past the cell cycle restriction point.
It is overactive or overproduced in neoplasms.
126
What is the function of RB in normal cells, and how is it changed in neoplasms?
Restrains cell proliferation by inhibiting passage through a restriction point.
Both copies are 'knocked out' in affected neoplasms.
127
Describe xeroderma pigmentosum.
Autosomal recessive, due to XP mutation.
Codes for a protein which is involved in DNA nucleotide excision repair.
The patients are therefore very sensitive to UV damage and develop skin cancer at a young age.
128
Describe hereditary non-polyposis colon cancer syndrome.
Autosomal dominant
Associated with colon carcinoma
Germline mutation which affects DNA mismatch repair genes.
129
Describe familial breast cancer
Assocated with BRCA1/2 genes which are important for repairing double strand DNA breaks
130
What is genomic instability in malignant neoplasms?
Alteration to the cell such as DNA mutations and abnormal chromosome segregation which accellerates the rate of mutation.
131
What are caretaker genes?
Genes which maintain genomic instability and are a class of tumour suppressor genes.
132
What is tumour progression?
The steady accumulation of multiple mutations
133
What are the six hallmarks of cancer?
```
Self-sufficiency in growth signals
Resistance to growth stop signals
Cell immortalisation
Sustained angiogenesis
Resistant to apoptosis
Ability to invade and produce metastasis.
```
134
What is Burkitt's lymphoma?
A lymphoma of B lymphocytes in germinal centres of the lymph nodes.
The B cells will all have identical IgH genes due to their clonal origin.
Characterised by disruption of the c-myc gene which has a role in cell cycle progression, apoptosis and cellular regeneration.
135
What is familial adenomatous polyposis (FAP)
Autosomal dominant mutation to APC which is a tumour suppressor gene.
Causes numerous benign colorectal polyps with an increased risk of colorectal carcinoma.
Adenocarcinoma likely to occur by 35 years old.
136
What is retinoblastoma?
Deletion of RB, a tumour suppressor gene. Seen in both familial and sporadic retinoblastoma.
Presents with visual loss, squint or enlargement of the eye.
Good prognosis as metastases are rare.
137
What is xeroderma pigmentosum?
Congenital deficiency of DNA repair enzymes.
Children exposed to sunlight will develop skin atrophy and tumours which are more characteristic of elderly people with long term sun exposure.
138
What is hereditary non-polyposis colorectal cancer?
Autosomal dominant mutations in MLH1 or MSH2 which are involved in DNA mismatch repair, significantly increasing risk of colorectal cancer without forming polyps.
139
What are the risk factors for bladder cancer?
beta-napthylamine
Cigarette smoking
Exposure to other specific chemicals
140
What are the risk factors for hepatocellular carcinoma and describe the progression.
Hepatitis B, aflatoxins, underlying cirrhosis
| Progression through pre-malignant lesions of dysplastic nodules.
141
What is malignant mesothelioma?
Primary is strongly associated with occupational exposure to asbestos and other fibrous material.
Begins as nodules in the pleura which extends to surround the lungs and causes fissures.
The chest wall is often invaded, causing severe and intractable pain.
142
What are the three anti-tumour defences?
Genes which act as guardians of the genome
Immune system
Non specific responses e.g. Inflammation
143
What are the normal activities of p53?
Prolongs the G1 phase of the cell cycle to allow extra time for correcting DNA defects
Triggers apoptosis and eliminates the faulty cell
Stimulates transcription of genes involved in differentiation so the cell is set on a path opposite to carcinogenesis
144
What condition can turn on p53?
Hypoxia
145
What can cause leukocytes to congregate in a tumour?
Chemotaxins secreted by tumour cells
Chemotaxins secreted by inflammatory cells
Chemotaxins secreted by necrotic tumour cells
Bacterial chemotaxins in ulcerated and infected tumours
Adhesion molecules expressed by the endothelium of tumour's vessels
146
Give a tumour which can spontaneously regress
Infant haemangioma
| Malignant melanoma
147
What are the most common childhood tumours?
Leukaemia
Nervous system
Bones
Testes
148
What cancer is related to aflatoxin?
Liver
149
What cancers is tobacco associated with?
```
Lungs
Mouth
Pharynx
Larynx
Oesophagus
Bladder
Pancreas
Cervix
```
150
What cancers can obesity predispose women to?
Endometrium
Gall bladder
Uterine cancer
151
What are some risk factors for breast cancer to do with sexual development?
Early menarche
Delayed first pregnancy
Induced abortion
First menopause
152
What cancer the Bence-Jones protein used to indicate when present in the urine?
Multiple myeloma
153
What causes an increase in prostate specific antigen in the blood?
Massage the prostate
Benign prostatic hypertrophy
Prostate cancer
154
What is carcinoembryonic antigen?
| Give a cancer that it cause it to be raised.
An oncofoetal protein which isn't significantly expressed in adults.
Colon carcinoma, pancreas, lung, rectal.
155
What carcinomas can cause a raise in alpha-fetoprotein?
Pancreas
| Stomach
156
What normally produces alpha-fetoprotein?
Liver
Yolk sac
Gastrointestinal epithelium?
157
Give some examples of chemotherapy agents?
```
Antimetabolites
Alkylating agents
Platinum based agents
Herceptin
Gleevec
Plant derived drugs
```
158
How do antimetabolites work in treating cancer?
Mimic normal substrates but can't be utilised.
159
Describe how alkylating and platinum based agents can be used in chemotherapy.
Cause x-linking of the DNA helix
160
Describe how plant derived drugs work as chemotherapy agents.
Inhibit microtubule assembly and interfere with mitotic spindle formation.
161
Describe how Gleevec works as a chemotherapy agent, with the cancer that it's used to treat.
Inhibits the overactive BCR-ABL protein produced in chronic myelogenous leukaemia due to the Philadelphia chromosome
162
Describe how herceptin works as a chemotherapy agent.
It inhibits HER2 receptors in breast adenocarcinomas which overexpress them.
163
What is important when predicting the outcome of a tumour?
Age
Health status
Tumour site, type, grade, stage
Availability of effective treatments
164
What is looked at to determine the extent of breast cancer using the Bloom Richardson system?
Tubule/gland differentiation
Mitoses number
Nuclear pleomorphism
165
What is the difference between an adjuvant and a neo-adjuvant in cancer treatment?
Adjuvant - after tumour excised to eliminate subclinical disease. Limits the possibility of a relapse.
Neo-adjuvant - tumour too large for surgery so need to shrink it first.
166
Why is chemotherapy administered in a number of small doses rather than one large dose?.
Normal cells recover faster so it reduces bystander damage
167
What can tamoxifen be used to treat in chemotherapy and how does it work?
Selective oestrogen receptor antagonist
| Treats breast cancer which is positive for the receptor.
168
What are some problems with cancer screening?
Lead time bias - appears that the patient survives longer, but is because the tumour is found earlier.
Length bias - more likely to detect slow growing tumours so appears better prognosis with detection
Over diagnosis - detects tumours which would never have become clinically relevant.
