Lecture 6 - Cancer Flashcards
what is Cancer?
what is Neoplasia?
Cancer is comprised of over 200 different diseases. At its most basic level cancer is abnormal cells that uncontrollably divide and never die. They accumulate together into clumps called tumours or flow freely through bone marrow, lymphatic fluid, body tissues and blood. These cancerous cells spread throughout the body via our efficient bloodstream invading other tissues.
Cancer can be compared with a parasite that drains energy from the body and competes for its nutrients.
Neoplasia: “new growth” denotes unregulated growth that is not controlled by normal regulatory mechanisms. These cells do not contribute whatsoever to an organism, but draw on its resources. Masses of these cells form together into clumps and are called “neoplasms” or “tumours”. They may be malignant or benign. The study of malignant cancer is Oncology.
6 unique characteristics of cancer cell?
Cancer cells have 6 unique characteristics that are different than any other cell in the body.
- Anaplasia
- Anchorage Independent
- Lack of Contact Inhibition
- Immortality
- Angiogenesis
- Genetic Instability
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1. Anaplasia: Dị sản
Cells become undifferentiated, meaning they have not developed into a particular cell yet. They have no function (other than reproducing). They possess a variety of cellular shapes and sizes, they have unusually large nuclei, and they bear little or no resemblance to the normal cells in the surrounding tissues.
- Anchorage Independent: Neo đậu
Cancer cells detach from the bottom of a culture flask, float away in soft agar and form new colonies, unlike normal cells that are usualy anchored. They also do not adhere easily to each other as normal cells do. These qualities encourage cancer cells to invade nearby tissue and expand outwards to go elsewhere in the body. - Lack of Contact Inhibition:
When normal cells contact each other or contact the basement membrane they attempt to move apart to avoid damage or collision. This is termed “contact inhibition”.
Cancer cells do not possess this normal cell trait. Normal cells cease(ngưng) to divide when they fill up the bottom of a flask and come into contact with the sides of the flask. Cancer cells continue to grow, even crowd and eventually pile up on each other, showing no signs of contact inhibition.
- Immortality bất tử
In normal cells, with each cell division, telomeres shorten until they are too short to protect the chromosomes and the cell dies. Telomeres protect the ends of our chromosomes and hold them together, they also aid in DNA copying when our cells divide.
Cancer cells reverse the shortening of the telomeres and lengthen their telomeres every time they divide, making them immortal. They may continue to divide for years with the right conditions.
- Angiogenesis: sự hình thành mạch
Tumours need a blood supply if they are to grow larger than a few millimeters. Cancer cells have the ability to secrete chemical stimulators that stimulate angiogenesis in the nearby tissues, thus developing a vascular network to bring oxygen and nutrients for continued growth and expansion of cancerous cells and a tumour.
- Genetic Instability:
Cancer cells divide continuously and also have a tendency (xu hướng) towards genetic alteration during cell division, which causes genetic damage. Cancer is often caused by damage to genes that help control cancer in the body like tumor suppressors (chất ức chế).
Classification of Tumours
Clinical classification of tumours: looks at the clinical presentation and outcomes of cancer
Histologic classification of tumours: looks under the microscope at cancerous tissues or cells, determines what type of cells the cancer is made up of.
Both are used together to correlate findings and to determine whether the cancer is benign or malignant.
- Benign cancer is defined by limited growth potential with a good prognosis or outcome, curable.
These are considered non cancerous tumours and may arise from any tissue type. They grow slowly and are usually encapsulated. If they continue to grow they take up space and compress or obstruct nearby organs or tissues, because of this they may need to be surgically removed.
Macroscopic vĩ mô : clearly separated from surrounding normal tissue, often encapsulated (đóng gói) so easily removed, may have expansive growth and may compress adjacent tissues or organs.
Microscopic vi mô : cells are similar to the original cells of the tissue invaded with high levels of differentiation, nuclei look more normal.
Cellular: uniform cell population (mostly all the same), similar nuclei to original cells, a well developed cytoplasm and functioning organelles, also have normal number of chromosomes.
Biologic: these cancerous cells may retain some of the complex functions of the original normal cells, and may stay localized
- Malignant cancer is defined by uncontrollable growth, and will eventually kill the host.
These are considered cancerous tumours. They are composed of cells with no function, other than to reproduce continually. There cells do not resemble giống the cells of the tissue of origin. These cancerous tumours do not have a capsule, this allows them to infiltrate (xâm nhập vào) normal tissues like the roots of a tree penetrating (thâm nhập) soil. The cells easily break away from the primary tumour site and flow away through the bloodstream, lymphatic vessels or nearby tissues causing metastatic (di căn) cancer.
Macroscopic: they lack a capsule so are difficult to remove. They are clearly separated from surrounding normal tissues and invade surrounding tissues like roots of a tree, penetrating throughout (infiltrative growth), can not be easily removed with surgery.
Microscopic: cells are very different from the original cells of the tissue invaded, they may exhibit new features that are not normal to the tissue cells invaded, this is called anaplasia.
Cellular: differing cell population, in size and shape also, the nuclei of these cancer cells are all different from each other, this is called pleomorphic (đa hình). They have reduced cytoplasm and organelles and an abnormal number of chromosomes
Biologic: They have no specialized function, these cancerous cells’ entire metabolism is geared (hướng) towards rapid growth and reproduction and they easily spread to other sites
- Metastasis (Di căn):
This is the process where tumour cells move from one site in the body to another site. Only malignant cells can spread.
Three main pathways for spread:
lymphatic system
bloodstream (hematogenous spread)
seeding of the surfaces of body cavities (close by)
- Metastatic Cascade: Dòng di căn
As the tumour grows, some cells develop the ability to metastasize (di căn), some do not
They enter the lymphatic system, blood stream or close-by cavities. The fluids in these systems carry the tumour cells away to a different site where they attach and begin forming a new tumour.
The cancerous cells must escape the immune system’s attack with T-lymphocytes, natural killer cells and macrophages
Must also form a new blood supply to bring oxygen and nutrients for the new tumour to grow, this is called angiogenesis (sự hình thành mạch)
Neoplasia
Tân sinh
Biology of a Tumour Cell
Biochemistry: a cancerous cell requires less oxygen, it has no other function besides reproducing, accumulating and spreading. It may even acquire new functions (anaplasia). It possesses a very simple metabolism.
Growth properties: survives easily, requires less nutrients, all energy goes to growth and reproduction, some cancer cells are immortal, they lack contact inhibition, they have anchorage dependant growth, they do not require external growth factors, some tumours produce their own, this is called autonomous (tự trị). The growth of tumour cells is excessive and unregulated because the tumour cells do not respond to normal inhibitory influences of neighbouring cells.
Cancerous cell growth has three distinct features that differentiate it from normal cell growth:
- Autonomous (tự trị) : it is independent of normal growth factors and inhibitors
- Excessive (Quá đáng): does not respond to normal growth & division regulators
- Disorganized: the tissues formed are irregular
When normal cells divide: the process is carefully regulated by the cells own genetic code, by signals transmitted from other cells and by chemicals that have growth inhibiting and/or growth promoting effects.
When neoplastic or cancerous cells divide: they have none of the above controls in place, they are not affected by other cells signals, they are not affected by other chemicals and they are disorganized.
Pathology - Neoplasia or Cancer
Classifications of Tumours
- Mesenchymal tumours
- Epithelial tumours
- Blood cell and lymphocyte tumours
- Tumours of neural cell precursers
- Tumours of glial cells
- Germ cell tumours
Khối u trung mô
Khối u biểu mô
Khối u tế bào máu và tế bào lympho
U tiền thân tế bào thần kinh
U tế bào thần kinh đệm
Khối u tế bào mầm
Benign Tumours - Naming
- Benign tumours from Mesenchymal cells (from connective tissue, bone and muscles) add “oma”.
Fibroma from fibroblasts
Chondroma from cartilage
Lipoma from adipose tissue
Leiomyoma from smooth muscle cells
Rhabdomyoma from striated muscle cells
Osteoma from bone
**Exception to the “oma rule”: lymphoma, glioma, seminomas are all malignant
- Benign tumours from Epithelial cells (from glands or ducts)
Adenoma
Tubular or villous - GI tract (polyps)
Papillomas - skin, urinary bladder, mouth, larynx
Cystadenomas - forms cysts
Malignant Tumours - Naming
- Malignant tumours of mesenchymal cells are named from the root of the cell type plus “sarcoma”
Fibrosarcoma - malignant tumour from fibroblasts
Chondrosarcoma - malignant tumour from cartilage
Liposarcoma - malignant tumour from fat - Malignant tumours of epithelial cells are called carcinomas
Squamous cell carcinoma - Malignant tumours of glands and ducts are called adenocarcinomas
Malignant tumours of embryonic cells (tế bào phôi) are called blastomas
Tumour Staging
We have two methods of staging or grading tumours:
1. TNM tumour staging
2. Grading a tumour
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1. Tumour Staging TNM:
Clinically assessing the extent to the tumour spread, using a clinical exam, X-rays, a biopsy or an exploratory surgery.
size of primary tumour (T)
presence or absence of lymph node involvement (N)
distant metastasis (di căn) (M)
Example: a tumour smaller than 2.5 cm that has spread to one local lymph node, but not to distant lymph nodes would be staged as: T1, N1, M0
- Tumour Grading: this is based on a histologic examination of tumour cells.
Grade I: well differentiated cells (benign)
Grade II: moderately well differentiated cells
Grade III: undifferentiated cells (malignant)
Causes of Cancer
- Causes of Cancer: carcinogens chất gây ung thư
I. Exogenous: from the outside world
chemicals, physical agents, viruses
II. Endogenous: from within us
in the genome (bộ gen) of each cell (oncogenes) gen gây ung thư
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1. Industrial carcinogens: workplace chemicals, examples: asbestos: lung cancer, naphthylamine: bladder cancer mining nickel: nasal cancers
- Drug carcinogens: some drugs although life saving have a low risk of cancer, example: chemotherapy
- Chemical carcinogens: natural or man made, example: polycyclic aromatic hydrocarbons found in cigarette smoke
- Physical carcinogens: mostly radiation from UV light (skin damage), X-rays, radioactive isotopes, atomic bombs
- Natural Biologic carcinogens: some fungi and parasites
- Viral carcinogens: RNA or DNA viruses
Human DNA Viruses linked to cancer
Human Papillomavirus (HPV): found in 60% of cervical cancer patients
Epstein-Barr Virus (EBV): Infectious Mononucleosis (kissing disease), very common, 90% of all people test positive for antibodies to it, may lead to Burkitt’s lymphoma or nasopharyngeal cancer
Hepatitis B Virus: liver cancer
Human T-Cell Lymphoma/leukemia (HTLV): in same group of viruses as HIV, causes leukemia
- Human Oncogenes Gen gây ung thư
Normal genes are transformed into proto oncogenes, by chromosomal rearrangement and the insertion of a viral genome
Tumour Suppressor Genes
Protect against activation of tumour cells and against excessive cell division
Immune Response to Cancer
Immune Response to Cancer:
Benign tumour cells are similar to original cells so do not invoke an immune response.
Malignant tumour cells change drastically and present to our immune system as a foreign invader would, they are called tumour antigens. Our cell mediated immune response is activated and limits growth of the tumour by using natural killer cells, macrophages and cytotoxic T lymphocytes.
Clinical Manifestations of Cancer
Clinical Manifestations of Cancer:
Highly variable depending on:
Type of tumour, location of tumour, histologic grade, clinical stage, immune status of host, sensitivity of tumour cells to therapy.
Presents with local symptoms or systemic symptoms
Unfortunately there are few early signs or symptoms for cancers. Often the symptoms are regional, related to where the tumour is and how fast it is growing
Local Symptoms: are caused by compression of adjacent tumours, or by a narrowed lumen due to a tumour, decreasing blood flow or blocking it completely.
Systemic Symptoms: Cachexia (a generalized wasting and weakness)
Weight loss
Thrombosis
Loss of appetite (anorexia)
Paraneoplastic syndromes (caused by cancer cell secretions)
Epidemiology of Cancer:
Epidemiology of Cancer: Study of cancer in human populations
- Incidence: number of new cases over a specific period
Cancer in Canada - 2019: Incidence and mortality (Tỷ lệ mắc và tử vong):
Incidence and mortality (Tỷ lệ mắc và tử vong)
Breast Cancer (women): 26,900 new cases, 5,000 deaths
Prostate (tuyến tiền liệt) Cancer (men): 23,300 new cases, 4,200 deaths
Lung Cancer (both sexes): 29,800 new cases, 21,200 deaths
Colorectal (đại trực tràng) Cancer (both sexes): 26,900 new cases, 9,700 deaths
(men have a 20% higher incidence)
- Prevalence: number of all cases in a specific population over a specific period
- Mortality: number of deaths in a specific population over a specific period
Cancer and Massage:
Benefits of Massage:
Benefits of Massage:
Reduced muscle tension or spasm, helps maintain muscle strength, increasing local nutrition to muscles and other tissues, promotes relaxation, improves sleep, decreases pain, increases immune function, prevents or reduces edema, decreases nausea and reduces fatigue. Overall increases quality of life. Self massage for neck and shoulder are also appropriate.
