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Questions and Answers
Which of the following characteristics is NOT associated with neoplasms?
Which of the following characteristics is NOT associated with neoplasms?
Familial cancers tend to arise later in life than sporadic cancers.
Familial cancers tend to arise later in life than sporadic cancers.
False
Balanced translocations can contribute to ________ by overexpression of oncogenes.
Balanced translocations can contribute to ________ by overexpression of oncogenes.
carcinogenesis
What are preneoplastic disorders?
What are preneoplastic disorders?
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What typically affects tumor suppressor genes in cancer?
What typically affects tumor suppressor genes in cancer?
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All cancers are inherited and non-sporadic.
All cancers are inherited and non-sporadic.
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What are oncogenes?
What are oncogenes?
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Match the following genetic alterations with their effects:
Match the following genetic alterations with their effects:
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What must happen to both copies of a tumor suppressor gene for tumor development to occur?
What must happen to both copies of a tumor suppressor gene for tumor development to occur?
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Malignant tumors do not invade adjacent structures.
Malignant tumors do not invade adjacent structures.
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What term describes a tumor that remains localized and does not spread to other sites?
What term describes a tumor that remains localized and does not spread to other sites?
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A benign tumor of glandular origin is called an ______.
A benign tumor of glandular origin is called an ______.
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Match the following characteristics with the type of tumor:
Match the following characteristics with the type of tumor:
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Which of the following is NOT a characteristic of malignant tumors?
Which of the following is NOT a characteristic of malignant tumors?
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Hyperplastic and dysplastic proliferations can lead to acquired preneoplastic disorders.
Hyperplastic and dysplastic proliferations can lead to acquired preneoplastic disorders.
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Chronic atrophic gastritis is an example of an ______ disorder.
Chronic atrophic gastritis is an example of an ______ disorder.
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What describes dysplasia in relation to cell structure?
What describes dysplasia in relation to cell structure?
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Metastasis refers to the primary growth of a tumor.
Metastasis refers to the primary growth of a tumor.
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What is the primary site for hematogenous spread of carcinomas?
What is the primary site for hematogenous spread of carcinomas?
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Tumor cell migration involves cell-derived cytokines, cleavage products of matrix components, and some ______.
Tumor cell migration involves cell-derived cytokines, cleavage products of matrix components, and some ______.
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Match the types of tumor spread with their descriptions:
Match the types of tumor spread with their descriptions:
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Which factor triggers angiogenesis in tumors?
Which factor triggers angiogenesis in tumors?
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E-cadherins help in maintaining cell-to-cell contacts in tumor cells.
E-cadherins help in maintaining cell-to-cell contacts in tumor cells.
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List one of the four stages involved in invasion of ECM by tumor cells.
List one of the four stages involved in invasion of ECM by tumor cells.
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Which of the following tumors is associated with mesenchymal origin?
Which of the following tumors is associated with mesenchymal origin?
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Malignant tumors are typically well differentiated and have slow growth rates.
Malignant tumors are typically well differentiated and have slow growth rates.
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What are MMPs, and what role do they play in tumor progression?
What are MMPs, and what role do they play in tumor progression?
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Benign tumors are usually __________ and have well-defined boundaries.
Benign tumors are usually __________ and have well-defined boundaries.
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Match the tumor types with their characteristics:
Match the tumor types with their characteristics:
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Which site is most commonly the first capillary bed encountered by metastatic tumors?
Which site is most commonly the first capillary bed encountered by metastatic tumors?
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Tumor markers like PSA can be used to screen for cancer and monitor recurrence.
Tumor markers like PSA can be used to screen for cancer and monitor recurrence.
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What sampling approaches exist for the diagnosis of tumors?
What sampling approaches exist for the diagnosis of tumors?
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Study Notes
Neoplasia
- New growth or abnormal outgrowing mass of tissue that does not coordinate with normal tissue
- May persist after stimuli cease
General Characteristics of Neoplasms
- Unresponsive to normal growth factors controlling cell division
- Compete with normal cells and tissues for metabolic needs
- Degree of autonomy steadily increases in size regardless of local environment and nutritional status of the host
- Require endocrine stimulatory signals for growth
Epidemiology of Cancer
- Incidence varies with age, race, geographic factors, and genetic background
- Most cancers are sporadic, but some are familial
- Familial cancers may be autosomal dominant or autosomal recessive
- Acquired diseases, known as preneoplastic disorders, are associated with an increased risk for development of cancer
Genetic Lesions in Cancer
- Tumor cells may acquire mutations through several means, including point mutations and chromosomal abnormalities
- Balanced translocations contribute to carcinogenesis by overexpression of oncogenes or generation of novel fusion proteins with altered signaling capacity
- Deletions frequently affect tumor suppressor genes, whereas gene amplification increases the expression of oncogenes
- Tumor suppressor genes and DNA repair genes may be silenced by epigenetic changes
Insensitivity to Growth Inhibitory Signals
- Tumor suppressor genes encode proteins that inhibit cellular proliferation by regulating the cell cycle
- Both gene copies must be dysfunctional for tumor development to occur
- In familial predisposition, affected persons inherit one defective copy of a tumor suppressor gene and lose the second one through somatic mutation
- In sporadic cases, both copies are lost through somatic mutations
Two Types of Tumours
- Benign: localized, not spreading to other sites, may produce local effects
- Malignant: can invade and destroy adjacent structures and spread to distant sites (metastasize)
Benign Tumours
- Resemble their normal cells of origin morphologically and functionally
- Well-differentiated cells
- Mitoses very scanty and normal configuration
- Grow slowly, localized, do not infiltrate
Acquired Preneoplastic Disorders
- Persistent regenerative cell replication
- Hyperplastic and dysplastic proliferations
- Chronic atrophic gastritis
- Chronic ulcerative colitis
- Leukoplakia of the oral cavity
- Villous adenomas of the colon
Nomenclature of Benign Tumours
- Cell type from which tumour arises + suffix “-oma”
- According to cells of origin, e.g.
- Adenoma: glandular pattern
- Papilloma: epithelial surfaces, producing microscopic or macroscopic finger-like structure
- Polyp: Mass projects above mucosal surface
- Cystadenomas: Hollow cystic masses
- Fibroadenoma of the breast and benign mixed tumour of salivary glands
Malignant Tumours
- Pleomorphism: variation in size and shape
- Hyperchromasia: Increased nuclear pigmentation
- High nuclear/cytoplasmic (N/C) ratio
- Giant cells may be formed containing several nuclei
- Nuclear pleomorphism, with coarse and clumped chromatin
- Numerous mitoses with atypical forms
- Loss of polarity: cells fail to form a recognizable pattern of orientation
- Dysplasia: loss in the uniformity of individual cells and their architectural orientation
- Rapidly growing tumour with progressive infiltration, invasion, destruction and penetration of the surrounding tissue
- Metastasis: secondary implants discontinuous with the primary tumour.
Pathways of Metastasis
- Seeding within body cavities
- Lymphatic spread typical for carcinomas
- Hæmatogenous spread for sarcomas, but carcinomas also metastasize by this route
- The liver and lungs are the most common secondary sites.
Mechanisms of Local And Distant Spread
- Invasion of ECM: reach the basement membrane, invade the interstitial connective tissue and penetrate the blood vessels’ basement membrane in four stages:
- Detachment of tumour cells from each other by loss of surface E-cadherins
- Attachment of tumour cells to matrix components
- Degradation of ECM by production and induction of fibroblasts to produce proteases
- Migration of tumour cells by cell-derived cytokines, cleavage products of matrix components and some growth factors
- Vascular dissemination:
- Intravasation: degradation of blood vessels’ basement membrane forming tumour emboli
- Extravasation of free tumour cells involves adhesion to the endothelium followed by transgression through the basement membrane
Development of Sustained Angiogenesis
- Vascularization of tumors is essential for growth and is controlled by the balance between angiogenic and antiangiogenic factors
- Hypoxia triggers angiogenesis through the actions of HIF-1α on the transcription of the pro-angiogenic factor VEGF.
- Several factors regulate angiogenesis; p53 induces synthesis of the angiogenesis inhibitor
Ability to Invade Tissues
- Loss of cell–cell contacts by the inactivation of E-adherin through a variety of pathways
- Basement membrane and interstitial matrix degradation is mediated by proteolytic enzymes secreted by tumor cells and stromal cells, such as MMPs
- Proteolytic enzymes also release growth factors sequestered in the ECM and generate chemotactic and angiogenic fragments from cleavage of ECM glycoproteins
- The metastatic site of many tumors can be predicted by the location of the primary tumor
- Many tumors arrest in the first capillary bed they encounter (lung and liver)
- Some tumors show organ tropism, probably due to activation of adhesion or chemokine receptors whose ligands are expressed by endothelial cells at the metastatic site
Nomenclature of Malignant Tumours
- Mesenchymal origin → sarcomas e.g. fibrosarcoma, chondrosarcoma, leiomyosarcoma
- Epithelial origin →carcinomas, e.g. squamous cell carcinoma, adenocarcinoma
- Two components (mesenchymal and epithelial) e.g. Teratomas → divergent differentiation into all embryonic layers, commonly seen in the ovaries and testicles, benign or malignant
Characteristics of Benign and Malignant Tumors
- Distinguished based on the degree of differentiation, rate of growth, local invasiveness, and distant spread.
- Benign tumors resemble the tissue of origin and are well differentiated; malignant tumors are poorly or completely undifferentiated (anaplastic)
- Benign tumors are slow-growing, whereas malignant tumors grow faster
- Benign tumors are well circumscribed and have a capsule; malignant tumors poorly circumscribed and invade the surrounding normal tissues
- Benign tumors remain localized to the site of origin; malignant tumors locally invasive and metastasize to distant sites
Laboratory Diagnosis of Cancer
- Sampling approaches for diagnosis: excision, biopsy, fine-needle aspiration, and cytologic smears
- Immunohistochemistry and flow cytometry studies help in diagnosis and classification of tumors
- Proteins released by tumors into the serum (tumor markers), such as PSA, can be used to screen populations for cancer and to monitor for recurrence after treatment
- Molecular analyses used to determine diagnosis, prognosis, detection of minimal residual disease, and diagnosis of hereditary predisposition to cancer.
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Description
This quiz examines the characteristics of neoplasia, including abnormal tissue growth that operates independently of normal cellular control. Explore the epidemiology of cancer, the factors involved in cancer incidence, and the genetic mutations that contribute to tumorigenesis.
