ONCOLOGY Flashcards
Differentiation
Each cell types differentiates and carries out particular functions.
The structure reflects the function of the tissue.
Mitosis
Part of the cell cycle
Requires genetic control—DNA and RNA
Mutation
If DNA in parent cell is altered and passed on, offspring cells will carry the mutation
Apoptosis
Programmed cell death
Controlled by genetic elements
Neoplasm or tumor
Cellular growth that no longer responds to normal genetic controls
Cell continues to reproduce, without need for them to reproduce
Deprives other cells of nutrition
Neoplasms may consist of atypical or immature cells.
Characteristics of each tumor depend on:
• Type of cell from which the tumor arises
• Unique structure and growth pattern
Defect in Cellular Proliferation
Most human tissues contain predetermined, undifferentiated stem cells.
Predetermined stem cells give rise to mature cells of the type of tissue where they reside.
All cells are controlled by an intracellular mechanism that determines proliferation.
Cancer cells grown in culture are characterized by loss of contact inhibition.
Grow on top of one another and on top of or between normal cells
Cancer cells respond differently from normal cells to intracellular signals regulating equilibrium.
Divide indiscriminately
Stem cell theory
Loss of intracellular control of proliferation results from mutation of stem cells.
DNA is substituted or permanently rearranged.
Once mutated
Cells can die from damage or by initiating programmed cellular suicide (apoptosis).
Can recognize damage and repair itself
Surviving mutated cells have potential to become malignant.
Two types of genes that can be affected by mutation are
1.Proto-oncogenes
Regulate normal cellular processes such as promoting growth
2.Tumour suppressor genes
Suppress growth of tumours
Function to regulate cell growth
Nomenclature
Benign tumors have tissue name plus the suffix -oma (e.g., adenoma)
Malignant tumors (cancers) have the tissue name plus the suffix -carcinoma (e.g., adenocarcinoma)
Tumors of connective tissue are usually termed sarcomas and are often malignant.
Several malignant tumors have unique names:
Hodgkin’s disease
Wilms’ tumor
Leukemia
Benign tumors
Usually differentiated cells that reproduce at a higher rate than normal
Encapsulated
Tissue damage
This is a result of compression of adjacent structures.
It can be life-threatening in the brain.
Malignant tumors
Undifferentiated, nonfunctional cells
Rapid reproduction—abnormal mitotic figures
Infiltrate or spread into surrounding tissue
Spread to distant sites
Malignant Tumors: Cancer
Lack control of mitosis and do not undergo apoptosis
No normal organization or differentiation
No contact inhibition
Abnormal cell membranes
Altered surface antigens
Do not adhere to each other
–Often break loose from mass
–Invade other tissues and may spread to distant sites
Mass compresses blood vessels.
—Leads to necrosis and inflammation around tumor
Tumor cells may secrete enzymes or hormones.
–Break down of proteins and cells
–Systemic effects, such as altered calcium levels
Inflammation and loss of normal cells
–Lead to progressive reduction in organ integrity and function
Angiogenesis
–Some tumor cells secrete growth factors.
• Stimulate the development of new capillaries in the tumor
Carcinogenesis
Process whereby normal cells are transformed into cancer cells
Process varies greatly with respect to time
Cancer is thought to be a multifactorial disease because of :
–Environmental effects
–Change in gene expression (heredity)
–Infection in some cases (e.g., cervical and hepatic cancers)
Some cancers have well-established risk factors.
Development of Cancer
Likely to be multifactorial
Origin of cancer may be: Genetic Chemical Environmental Viral or immunological From causes not yet identified
Development of Cancer (Cont.): initiation
Mutation of cell’s genetic structure
• From inherited mutation (an error during DNA replication)
• From exposure to a chemical, radiation, or viral agent
Mutated cell has the potential to develop into clone of neoplastic cells
Once initiated, mutation is irreversible.
Not all mutated cells form a tumour.
Mutated cells become tumours only when they establish the ability to self-replicate and grow.
Carcinogens may be:
- Chemical
- Radiation
- Viral
Carcinogens can be:
- Detoxified (by protective enzymes)
- Harmlessly excreted
Cells damaged by carcinogens may:
- Self-repair
- Die
- Replicate into daughter cells with same genetic alteration
Development of Cancer
1. Chemical carcinogens
- -Long latency period makes identification of carcinogens difficult.
- -Animal studies may not apply to humans.
- -Certain drugs have been identified as carcinogens.
Development of Cancer
2.Radiation
- -Ionizing radiation can cause cancer in almost any human tissue.
- -Dose of radiation needed to cause cancer is unknown.
- –Ultraviolet radiation is associated with melanoma and squamous and basal cell carcinoma.
Development of Cancer (Cont.)
3. viral carcinogens
ie. Epstein-Barr virus (EBV)= Burkitt’s lymphoma
Development of Cancer (Cont.)
PROMOTION
Process leads to tumor development Activities of promotion are reversible: • Obesity • Smoking • Alcohol • Dietary fat • Hormones • environmental chemicals Cause further changes in DNA Less differentiation and increased rate of mitosis and/or lack of apoptosis Dysplasia or anaplasia may be evident.
Development of Cancer (Cont.)
LATENT PERIOD
- -May range from 1 to 40 years
- -Length of latent period associated with mitotic rate of tissue of origin and environmental factors
- -For disease to be clinically evident, tumour must reach a critical mass that can be detected.
Development of Cancer (Cont.)
PROGRESSION
Characterized by • Increased growth rate of tumour • Invasiveness • Metastasis Most frequent sites of metastasis are lungs, brain, bone, liver, and adrenal glands.
Metastasis process begins with rapid growth of primary tumour
• Develops its own blood supply
—-Critical for survival and growth of tumour
• Tumour angiogenesis is formation of blood vessels within tumour
• Certain segments of primary tumour can detach and invade surrounding tissues
• Detached cells can invade lymph nodes and vascular vessels to travel to distant sites.
• Most mobile tumour cells do not survive.
• Surviving tumour cells must create an environment conducive to growth and development.
Immunity and Cancer Risk
—Cell-mediated immunity recognizes some tumor cells and destroys them.
—Immunization for cervical cancer and hepatitis is recommended to reduce cancer risk from infection.
Risk Factors
Genetic factors
–Oncogenes that regulate all growth
Viruses
–Oncoviruses alter host cell’s DNA.
Radiation
–Ultraviolet rays, X-rays and gamma rays, Radioactive isotopes, Risk is increased with higher cumulative dosage.
Chemicals (check health and safety information)
–Organic solvents, Asbestos, Heavy metals, Formaldehyde, Chemotherapy agents
Biological factors
–Chronic irritation and inflammation, Age, Diet,, Hormones
Risk Reduction
Limit UV exposure from sun or tanning booths.
Regular medical and dental examinations
Self-examination
Diet:
- Increased fiber content
- Reduced fats
- Five to ten servings of fresh fruits and vegetable daily. These foods contain antioxidants, which reduce changes in DNA.
Warning Signs of Cancer
- anemia
- change in bowel movements
- a sore that does not heal
- weight loss
- cough
Local Effects of Tumors
—-Pain
May be absent until very late stages
Occurs when tumor is well advanced
Severity depends on the type of tumor
—-Obstruction
Occurs wen tumor compresses a duct or passageway
Blood supply or lymphatic flow may be restricted
Digestive tract
Airflow in bronchi
——Tissue necrosis and ulceration
May lead to bleeding or infection around the tumor
Systemic Effects of Malignant Tumors
Weight loss and cachexia (ca-KeK-Sia): Anorexia, fatigue, pain, stress. Increased demands on the body from tumor cells
Anemia: Caused by blood loss at tumor site,Nutritional deficits may reduce hemoglobin synthesis.
Severe fatigue: Caused by inflammatory changes, cachexia, anemia, Stress of treatment schedule, Psychological factors
Effusions : Inflammation causes fluid buildup in body cavities.
Infections: Occur frequently as resistance declines
Bleeding: Tumor cells may erode the blood vessels.
Paraneoplastic syndrome: Associated with certain tumor types, Tumor cells release substances that affect neurological function and may have hormonal effects.
Diagnostic Tests
–Routine screening
Essential for early detection
Following treatment to detect any further tumors
–Self-examination
Early detection if done consistently
Breast, testicular, and skin examinations are important.
–Blood tests
Measure blood cell levels during treatment
May detect tumor markers (e.g., PSA test)
–Radiographic, ultrasound, MRI, CT
–Methods of visualizing changes in tissues or organs
–Cytological tests require biopsy or cell sample
Histological and cytological examinations to determine degree of differentiation and tumor type
May be tested for growth promoter sensitivities, (e.g., estrogen-dependent tumors)
Most dependable confirmation of malignancy
