Podcast
Questions and Answers
What is the primary characteristic that differentiates malignant neoplasms from benign neoplasms?
What is the primary characteristic that differentiates malignant neoplasms from benign neoplasms?
Which type of mutation is responsible for the majority of cancers?
Which type of mutation is responsible for the majority of cancers?
How many genetic changes are typically required for a normal cell to transform into invasive cancer?
How many genetic changes are typically required for a normal cell to transform into invasive cancer?
Which of the following is NOT an example of an environmental factor that can induce mutations leading to cancer?
Which of the following is NOT an example of an environmental factor that can induce mutations leading to cancer?
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What is the primary focus of oncology?
What is the primary focus of oncology?
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What process allows cancer cells to continue dividing uncontrollably once they reach other cells?
What process allows cancer cells to continue dividing uncontrollably once they reach other cells?
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How do cancer cells achieve resistance to cell death?
How do cancer cells achieve resistance to cell death?
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What role does tumor angiogenesis play in cancer progression?
What role does tumor angiogenesis play in cancer progression?
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What is the fundamental reason cancer cells can undergo unlimited replication?
What is the fundamental reason cancer cells can undergo unlimited replication?
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Which of the following statements about tumor suppressor genes is correct?
Which of the following statements about tumor suppressor genes is correct?
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Study Notes
Neoplasms
- Neoplasia means "abnormal new growth"
- A tissue mass formed by this abnormal growth is called a neoplasm or tumor
- Neoplasms result from uncontrolled cell proliferation
- Oncology is the study of tumors or neoplasms
- Neoplasms are classified into benign and malignant (cancer)
Benign vs. Malignant Neoplasms
- Benign neoplasms grow slowly, are non-invasive, and do not metastasize
- Malignant neoplasms grow quickly, are invasive, and can metastasize
Biological Mechanisms of Cancer
- Cancers arise from non-lethal genetic damage or gene mutations
- Multiple genetic changes (at least 4-7) are needed for a normal cell to become an invasive cancer
- First, second, third, and fourth mutations occur (shown pictorially)
Causes of Genetic Changes
- Inherited: Germline mutations (rare familial cancers, account for ~10% of cancers)
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Acquired: Somatic mutations (sporadic), induced by environmental factors
- Physical agents: UV rays (sun exposure), X-rays
- Chemicals: tobacco products, dietary chemicals, toxins
- Infectious agents: bacteria, viruses
Examples of Cancers from Environmental Exposures
- UV rays: skin cancers (skin melanin protects)
- HPV (human papilloma virus): cervical cancer
- Hepatitis B virus: hepatic carcinoma
- Helicobacter pylori: gastric carcinoma
- Tobacco products: lung cancer, urinary bladder cancer
Cancer Arising from Single Cells
- Tumors form from the expansion of a single cell with genetic damage (clonal)
- Daughter cells have the same abnormal DNA, and continue accumulating damage
- Cancer hallmarks are produced by a series of mutations during progression
Hallmarks of Cancer (Biological Criteria)
- Independence (Self-sufficiency in growth signals): Cancer cells don't need growth factors to divide; they grow autonomously
- Resistance to Anti-growth Signals (mutated tumor suppressor genes): Tumor suppressor genes (e.g., retinoblastoma gene, p53 gene) are impaired, enabling continuous cell division.
- Loss of Contact Inhibition: Cancer cells continue to grow even after contacting other cells, forming a mass (tumor)
- Unlimited Replication (telomeres): Normal cells divide a limited number of times due to telomere shortening. Cancer cells have activated telomerase, an enzyme that elongates telomeres, allowing unlimited divisions (immortality).
- Resistance to Cell Death (Evasion of Apoptosis): Cancer cells resist programmed cell death (apoptosis) even with DNA damage or abnormalities, allowing them to proliferate
- Sustained Angiogenesis: Cancer cells induce the formation of new blood vessels (angiogenesis) to provide nutrients and oxygen for growth and metastasis
- Invasion and Metastasis: Cancer cells invade surrounding tissue and spread (metastasize) to other parts of the body. Steps include loss of intercellular adhesion, extracellular matrix degradation, and cell movement (pseudopodia). Metastatic sub-clones carry more mutations
- Altered cellular metabolism
- Evasion of host immune response
- Drug resistance
Reference
- Robbins & Cotran Pathologic Basis of Disease (9th edition, 2014) (ISBN details provided)
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Description
Explore the key concepts of neoplasms and their biological mechanisms, including the differences between benign and malignant tumors. This quiz covers the causes of genetic changes leading to cancer and the role of inherited versus acquired mutations. Test your knowledge of oncology and neoplastic growth.
