Case 4- colon cancer, staging and screening Flashcards
Why is grading and staging important
Useful for evidence-based prognosis and may indicate different treatment. Helps communication between health professionals as you don’t have to describe the cancer in detail
Cancer grading
Histological and is based on tissue samples from a biopsy, looking at how aggressive the cancer is. It looks at the degree of differentiation between the tumour and normal tissue. Tumours which are poorly differentiated will be very different to normal tissue and will be more aggressive.
How can degree of differentiation be determined by
- Mitotic activity- more aggressive tumours will have increased mitotic activity
- Nuclear size- more aggressive tumours will have increased DNA replication meaning that the nucleus size within cells increases
- Hyperchromasia (how dark the nucleus is)- increased DNA replication in aggressive tumours causes the nucleus to appear darker when looked at under the microscope, as it contains more DNA than usual
Bowel cancer grading
GX - cannot be identified - for example the tissue sample may not have been labelled correctly
G1 - well differentiated
G2 - moderately differentiated
G3 - poorly differentiated
G4 - undifferentiated (anaplastic tissue)
Cancer staging
Is anatomical and is based on scans, it looks at how widespread the cancer, will also look at its size and if it entered the lymphatic system
Most common staging method
TNM is the most common staging method, it stands for tumour size, nodal involvement and metastases. It will be written in the format T2N1M0
Staging tumour size guide
TX- tumour size cant be assessed, no scans or imaging T0- no tumour present Tis- ‘tumour in situ’. The tumour has malignant potential, the biopsy shows increased mitotic activity or an enlarged nuclei, but the tumour has not yet invaded through the basement membrane. T1- into submucosa T2- into muscularis propria T3- into subserosa T4a- into visceral peritoneum T4b- attached to other organs/structure
Staging nodal involvement
NX- cant be assessed
N0- no lymph nodes involved
N1- 1 single lymph node involved or more then one lymph node is involved but they are all part of the same group of lymph nodes
N2- more then one group of lymph nodes affected
Staging metastases involvement
M0- no metastases present
M1- metastases are present (either one or multiple)
Stage 0-4 cancer
A stage 0 cancer is one where the tumour is in situ (has malignant potential but hasn’t invaded through the basement membrane. Stages 1, 2 and 3 show that there is local growth and spread. In stage 4 there is distant metastases.
Screening and public health
Screening is a part of secondary disease prevention. It helps identify a disease at its early stage so it can be more easily managed
Types of prevention
Primary prevention- reducing the risk of a disease i.e. immunisation or banning toxic substances
Secondary prevention- identification/ management of an early disease i.e. screening and self-breast examinations by women
Tertiary prevention- prevention of chronic and disabling effect of a disease i.e. chronic disease management programmes and support programmes
Screening
Not a diagnostic procedure but instead identifies apparently healthy people who are at an increased risk of a disease or a condition. They can then be offered information, further tests and appropriate treatment to reduce their risk and/or any complications arising from the disease or condition.
Fetal anomaly screening programme
Screens for 11 structural anomalies including down’s syndrome. Multiple tests done between 10 and 20 weeks
Infectious diseases in pregnancy screening (IDPS) programme
Offers testing for hep B, HIV and syphilis. Usually done at 10 weeks
New-born and infant physical examination (NIPE) screening programme
Screens new-borns within 72 hours and at 6-8 weeks after birth, including hips, eyes and hearts
New-born blood spot (NBS) screening programme
Heel prick test at 5 days old. For sickle cell, CF, congenital hypothyroid, inherited metabolic diseases, e.g phenylketonuria, MCADD
New-born hearing screening programme (NHSP)
Offered to all babies within 4-5 weeks to test hearing
Sickle cell and thalassaemia (SCT) screening programme
All pregnant women in England are offered a blood test to find out if they carry a gene for thalassaemia. Those at high risk of being a sickle cell carrier are offered a test for sickle cell.
Diabetic eye screen
Yearly retinal exam of all people with a diagnosis of diabetes over age 12
Bowel cancer screening
FIT tests for all adults aged 60-74, every two years. gFOB test is also used. In the FIT test the end of a stick is dipped into a single bowel motion, replaced in a tube and returned in a prepaid envelope
Cervical cancer screening
LBC test for all women. Aged 25-49, every 3 years. for those aged 50-64 it’s every 5 years
Breast cancer screening
Mammogram all women aged 50-70, every 3 years, and self refer>70 years.
NHS health check screening
Adults between the age of 40-74 get this test every 5 years. It checks your lifestyle and family history, height and weight, blood pressure and blood test. It uses an algorithm to provide a risk assessment for a CVD event in the next 5 years. It screens for diabetes, heart disease and stroke.
Genetic screening
Done under certain circumstances to inform reproductive choice, identifies risk factors and can inform preventative action (BRCA). Can also be used in antenatal screening and IVF pre-implantation genetic testing.
The three main categories of screening
Proactive screening which can be targeted, regular breast exams between 50 and 70, or untargeted, all new-borns get a physical exam. Voluntary screening is by patient request i.e. prostate cancer. Opportunistic screening is if you got a cholesterol test because you were visiting the GP.
The 4 criteria’s for implementing a screening test
The disease, the screening test, diagnosis and treatment, the programme
Screening test criteria- the disease
Needs to be a common and serious health problem. There needs to be a strong link between the risk factors of the disease marker you are testing and the actual disease
Screening test criteria- the screening test
Test must be valid (sensitive and specific), simple, cheap, safe, acceptable and reliable. If the test is not acceptable to the patient there will be a low uptake. Sensitivity is about correctly identifying those who have the disease (true positive) whilst specificity is about identifying those who don’t have the disease (true negative).
Screening test criteria- diagnosis and treatment
An agreed policy and appropriate treatment options for those who test positive. The facilities must be adequate to meet the demand of the treatment.
Screening test criteria- the programme
There must be evidence that the screening programme is beneficial and reduces disease and mortality. It must be acceptable to the public and healthcare professionals whilst being cheap. There must also be the appropriate facilities in place with quality assurance.
The principles of Cancer surveillance
About analysing and collecting data in order that action may be taken. There should be systematic collection of data for cases, analyses of data and stats and distribution of this data. In the UK all cases of cancer are registered on the national cancer registration
Colonic carcinoma- inherited
Under 10% of colonic carcinoma cases have a true inherited disposition, 1% is FAP (inherited mutations in the APC mutation gene, they get polyps which develop into cancer at 40) and 2-5% HNPCC (Lynch syndrome- due to mutations in DNA repair genes).
Colonic carcinoma risk factors
Being over 50, previous CRC (the colonic epithelium will be unstable), strong family history of CRC. Previous adenomatous polyps, longstanding IBD (inflammatory bowel disease such as Crohn’s or ulcerative colitis, the risk is proportional to how long you have had the disease and how much of the bowel is affected), inherited syndromes, type 2 diabetes and an unhealthy lifestyle. You reduce your risk by eating high fibre fruit and veg, as low fibre and red meat increase the amount of time faecal matter is in the colon. Red meat consumption, smoking and alcohol consumption increase the risk.
Pathology of colon cancer
Highly proliferative epithelium, adenoma, adenocarcinoma
Symptoms of right sided colon cancer
Tiredness, weight loss, anaemia, occult bleeding and RIF mass
Symptoms of left sided colon cancer
Tiredness, weight loss, colicky pain, rectal bleeding, bowel obstruction, tenesmus, LIF mass and change in bowel habits
How the gut is separated
The gut is split into the foregut, the midgut and the hindgut. The left side of the colon is hindgut and most of the right side is in the midgut. Right colon cancer tends to cause pain around the umbilicus and the left colon cancer causes pain in the hypogastrium/suprapubic.
Why do cancers in the right colon tend to grow larger
There is lots of space for the cancer to grow into without causing obstructive symptoms, such as bloating or pain. The faecal stream is liquid so is able to move through a small space.
Why is colon cancer associated with Iron deficient anaemia
As the cancer grows it is supplied by blood vessels, these vessels are very fragile and tend to bleed. The blood will mix with the fecal stream and not be visible. So cancers on the right side wont show their bleeding but will deplete the bodies iron stores leading to anaemia.
What type of anaemia is iron deficient anaemia
Microcytosis with small red blood cells
Why is colon cancer a good candidate for a screening programme
The earlier you pick up bowel cancer the more treatable it is, i.f you have a positive screening test a colonoscopy will be performed
Mechanism of bowel cancer
Go through a pre-malignant stage before they become cancerous. They start at adenomas which are benign growths. There is a mutation in the APC gene (tumour suppressor gene) which leads to uncontrolled growth of the epithelium (Hyperproliferative epithelium). Then there is a K ras and DCC mutation which causes an adenoma. Then a p53 mutation which creates a carcinoma.
Appearance of a non-benign adenoma
The cells will not be regular, some patches will be more vascular then others and the centre will be sunken suggesting the scar tissue is pulling the polyp down. The basement of the epithelium will be a lot less clear
Treatment for colon cancer
At the T1 stage the tumour may be removable though endoscopy and wont require surgery. Fluid can be injected in the submucosal space, this will lift the polyp free of the bowel wall. A snare can be placed over the polyp and then it can be removed
Testing for colon cancer
You can use a faecal immunochemical test (FIT) to detect blood in your stool, tests for Globin so you don’t get false positives. You will also do a blood test to detect number of red and white blood cell. You will then have a colonoscopy to confirm the cancer, take a biopsy to confirm the microscopic factors. CT colonoscopy can provide x-ray pictures.
Polyps
Mass of cells that grow in the inner lining of the colon.
Haemorrhoids
Swollen veins in the lower part of the rectum or anus
Fissure
A cut or tear in the anus
Diverticular disease
The growth of small sacs in the colon due to weakening of the lining, they protrude outwards
Ulcerative colitis
Swelling of the colon and rectum
Carcinoma
Cancers derived from epithelial cells
Sarcoma
Cancers derived from connective tissue, originating in mesenchymal cells
Lymphoma
Cancer forming from blood forming cells that tend to leave the bone marrow and mature in the lymph nodes and blood
Blastoma’s
Cancers derived from immature precursor cells or embryonic tissue
