What is Cancer?

A general term for a large group of diseases characterized by uncontrolled growth of abnormal cells.

Cellular Growth

Neoplasm: Any abnormal growth. May be benign or malignant, but the term is generally used to describe cancer.

Hypertrophy: Enlargement of a tissue or organ because of the enlargement of individual cells.

Hyperplasia: Increase in the size of a tissue due to the increase in the absolute number of cells.

Cell Differentiation (quality)

Metaplasia: A uniform and predictable change in cell type that is predictable, physiological and often reversible.

Dysplasia: An abnormal degree of variation, size, shape and appearance occurring in cells. Often non-physiological and irreversible.

Differences in Cancer cells and Normal cells

Structural:

•Chromosomal abnormalities

•Irregular shape and size

Differences in Cancer cells and Normal cells

Functional:•Loss of production of specialized proteins

•Modified contact inhibition

•Altered surface antigens

•Very high metabolic requirements

•Release of angioplastic substances to stimulate growth

Benign Tumors

Characteristics:•Expand by simple local growth

•Plateau

•Become encapsulated

•Smooth borders

Effect on Host:•Compression

•Constriction

•Ulceration

•Hypersection

Malignant Tumors(Carcinoma-epithelial; Sarcoma-bone, muscle, connective)

Characteristics:• Rapid growth

• Loss of specialization

• Neither cohesive or encapsulated

• *Patterns of metastasis are usually predictable via blood vessels or lymph channels

Malignant Tumors

Effects on Host:

•Effects of benign tumors

•Weight loss

•Wasting of tissue

•Anemia

•Electrolyte & fluid imbalances

•Malnutrition

How do cells become malignant?The process appears to occur as multi-stage process.

INITIATION: Conversion of cells to those with neoplastic potential (DNA changes as a result of exposures to carcinogens)

PROMOTION: Some form of chronic irritation that accelerates the rate of growth of already abnormal cells

How do cells become malignant?

CARCINOGENIC SUBSTANCES (MUTAGENS):

May influence cells to become malignant in a number of ways:

•Change the structure of cellular DNA (mutation)

•Add genetic information (viruses may act in this manner)

•Depress oncogenes and turn on existing genetic codes.