Neoplasms and Tumor Characteristics Quiz

Neoplasia I - Session 9

• Neoplasia is a general term for abnormal cellular growth
• Tumors are a swelling resulting from any cause—inflammation, trauma or abnormal growth
• Neoplasm specifically refers to abnormal cellular growth that persists after initiating stimulus is removed
• Cell growth that does not respond to normal regulatory mechanisms is indicative of a neoplasm
• There are benign and malignant neoplasms

Benign Neoplasm

• Cells grow in a compact mass
• Remain at the site of origin
• Example: colonic adenoma

Malignant Neoplasm

• Cell growth is uncontrolled
• Cells can spread into surrounding tissue and to distant sites
• Cancer is a malignant neoplasm

Cancer Characteristics

• Cancer is a genetic disorder due to DNA mutations
• Mutations can be from spontaneous causes or environmental insults
• These mutations are heritable and passed on during cell division
• Cells with these alterations are subject to Darwinian selection
• The changes in DNA cause an alteration in cell growth and behaviour
• Oncogenes and tumor suppressor genes are altered
• Gene alterations happen from normal to benign to malignant

Immunological Theory of Cancer

• Immune system surveys and destroys cancerous cells
• Tumorous cells may remain undetected and dormant during a period of “equilibrium”
• In the escape phase, tumors overpower immune system and spread

Somatic Mutation Theory of Cancer

• Analysis of cancer development through genetic factors
• Specific mutations directly correlate with specific cancers

Stem Cell Theory of Cancer

• Cancer is a result of unregulated stem cell growth

Tumor Progression

• Multiple mutations lead to colon cancer
• Genetic changes result in tumor changes

Clonality

• The change must be non-lethal and passed to daughter cells
• Therefore, genetic alterations exist in every cell of a monoclonal population
• Initially demonstrated using enzyme G6PD encoded on the X chromosome

Neoplastic vs Normal Cells

• Growth control is altered: Proliferation is stimulated while cell death is suppressed
• Factors which regulate growth, including receptors, are altered
• Cellular interactions between cells, and with stroma, are also altered

Growth Control

• Increased cell proliferation: more cells enter cell cycle, cycle is speeded up

• Cells have changed life span due to decreased apoptosis

• Modifications in cell metabolism

• Angiogenesis is altered

• In normal tissues, the rates of new cell growth and old cell death are in balance

• In cancer, this balance is disrupted

• This disruption can lead to uncontrolled cell growth or loss of a cells’ ability to undergo apoptosis

Growth Control (Altered synthesis of growth factors)

• Autocrine or paracrine effect altered
• Altered receptors—increased, decreased, mutated
• Excess/modified growth control proteins

Cellular Interactions

• Cell-cell interactions
• Cell-stromal interactions (e.g., with the basement membrane)
• Important for differentiation, embryogenesis, and growth regulation in normal cells

Differences Between Benign and Malignant Neoplasms

• Size
• Growth characteristics
• Vascularity/necrosis
• Function
• Invasion/metastasis

Differentiation

• How close the parenchymal cells resemble the normal cells of the type
  • more differentiated cells retain more functional capabilities of the normal counterparts, benign tumors usually have well-differentiated cells.
  • Lack of differentiation is designated as anaplasia,
    • anaplasia includes bizarre nuclei, atypical mitoses, loss of polarity,
    • more rapidly growing tumors that are more anaplastic less likely to have specialized function activity

In-situ Malignancy

• Epithelial neoplasm shows evidence of malignancy—altered cell growth, cytological atypia, altered differentiation
• BUT no basement membrane invasion

Possible Events

• Benign to Benign
• Benign to Dysplasia
• Benign to Dysplasia to In-situ
• Benign to Dysplasia to In-situ to Invasive
• Dysplasia to In-Situ to Invasive
• In-situ to Invasive
• Invasive to Invasive

Nomenclature

• Tumors composed of stroma (supporting connective tissue, blood supply) and parenchyma (neoplastic cells, which determine biologic behavior)
• Named according to parenchyma, organ, or cell type (e.g., Hepatoma- liver, Osteoma-bone)
• Named according to pattern or structure (e.g., Fluid-filled → CYST, Glandular → ADENO, Finger-like → PAPILLO, Stalk → POLYP)

Types of Neoplasms (Benign vs Malignant)

• Benign: Epithelial, Connective tissue, Lymphoid/haemopoietic, Germ cell
• Malignant: Epithelial, Connective tissue, Lymphoid/haemopoietic, Germ cell