Chapter 1 : Introduction 

Topics covered in this snack-sized chapter:

• Introduction

• Different Kinds of Cancer

• How Do Normal Cells Become Cancerous?

• How Do Cancer Cells Grow?

• What Do Cancer Cells Look Like?

• Tumor

• Benign vs. Malignant

• Why Is Cancer Dangerous?

• Cancer: a term for diseases in which normal cells become abnormal and divide without stopping, sometimes invading other tissues

• Cancer cells can spread to other parts of the body through the blood and lymph systems.

• There are more than 100 different types of cancerous diseases

• Carcinoma:

• Cancer that begins in the skin or in tissues that line or cover internal organs

• Examples: bladder, brain, breast, cervical, colorectal, endometrial, kidney (renal), lung, melanoma (skin), ovarian, pancreatic, prostate and thyroid

• Sarcoma:

• Cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue

• Leukemia:

• Cancer that starts in blood-forming tissue such as bone marrow and enters the bloodstream

• Lymphoma and myeloma:

• Cancers that begin in the cells of the immune system and lymph nodes

• Central nervous system cancers:

• Cancers that begin in the tissues of the brain and spinal cord

• There are many processes that control a cell’s growth and division.

• Several of the control mechanisms need to be damaged before a cell becomes cancerous.

• Cancer arises from a loss of normal growth control.

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

• In cancer, this balance is disrupted.

• This disruption can result from uncontrolled cell growth or loss of a cell's ability to undergo cell suicide by a process called "apoptosis."

• Apoptosis, or "cell suicide," is the mechanism by which old or damaged cells normally self-destruct.

• Tissue square 1 (top left): when a normal cell dies, the body replaces it with another normal cell (pink-colored cell)

• Tissue square 2 (middle square): cancer cells grow in an uncontrolled manner; they fail to die and therefore the diseased cells accumulate and form a mass or "tumor" (Green-colored cell)

• Tissue square 3 (bottom right): the malignant cells multiply until a mass of cells (a tumor) is created

• Cancer cells invade nearby tissue and/or blood vessels.

• Tumors remain small until they're able to attract their own blood supply (angiogenesis), which allows them to obtain the oxygen and nutrients they need to grow larger.

• Cancer tissue has a distinctive appearance under the microscope.

• Among the traits a doctor looks for are:

• A large number of irregularly shaped dividing cells

• Variation in the size and shape of the cell nucleus

• Variation in cell size and shape

• Loss of specialized cell features

• Loss of normal tissue organization

• A poorly defined tumor boundary

• Increase in the number of undifferentiated cells creates a growing mass of tissue called a "tumor" or "neoplasm."

• Not all tumors are cancerous; tumors can be benign or malignant.

• They can often be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body.

• Cells in malignant tumors are abnormal and divide without control or order.

• Cancer cells invade and destroy the tissue around them.

• Cancer cells can also break away from a malignant tumor and enter the bloodstream or lymphatic system.

• Cancer refers to any one of a large number of diseases characterized by the development of abnormal cells that divide uncontrollably.

• Many cancers have the ability to infiltrate and destroy normal body tissue and organs.

• When cancer cells spread throughout the body, this is called metastasis. Once cancer metastasizes, it may become deadly.

• Depending upon the type and location of the disease, the presence and growth of cancer can be dangerous.