Chapter 19

Introduction

  • cancer is a disease caused by abnormal and excessive growth of cells in the body

  • cancer cells accumulate and compress, invade, and ultimately destroy the surrounding normal tissue

  • about 550,000 people die from cancer each year

Characteristics of Tumors

  • Tumors are new growths that arise from normal tissue

  • malignant: tumors that are invasive and spread

    • multiply rapidly

    • invasive into normal tissue

    • composed of cancerous cells that resemble primitive cells but lak the ability to perform mature cell functions

    • anaplasia: backward growth

    • Undifferentiated (dedifferentiated): reverting to a less specialized state

    • Hyperchromatic:

    • Metastasis: a secondary growth

  • benign: non-invasive and don’t spread

    • grow slowly

    • often encapsulated so they don’t invade surrounding tissue

    • closely resemble normal mature tissues

    • nonmetastatic

carcinogenesis

  • Carcinogenesis: transformation from a normal cell to a cancerous one

  • malignant transformation results from damage to the genetic material (DNA)

  • strands of DNA form Chromosomes

  • DNA (Gene)

    • Controls the production of new cells (cell division which is known as Mitosis)

    • controls the production of new proteins (Protein synthesis)

      • protein carries out an important specific function to the cell

  • When a cell becomes malignant, however, the processes of mitosis and protein synthesis are disturbed. Cancer cells reproduce almost continuously, and abnormal proteins are made. Malignant cells are anaplastic; that is, their DNA stops making normal codes that allow the cells to carry on the function of differentiating mature cells.

  • some mutations found in cancer cells prevent the cells from dying

  • environmental agents

    • chemicals, drugs, tobacco smoke, radiation, and viruses can cause damage to DNA and thus produce cancer (Carcinogens)

    • Chemical carcinogens: cigarette, cigar, pipe smoke, automobile exhaust, insecticiede, dyes, industrial chemicals, some insulations, hormones (estrogen can cause cancer by stumulating growth of cells in the lining of the uterus or in milk glands in the breast

    • Radiation: Sunlight, x-rays, radioactive substances

    • viruses: Human T cell leukemia, HPV, Hep B and C

  • oncogenes

    • pieces of normal DNA that when activated by a mutation, can convert a normal cell to a cancerous cell.

    • ras: colon cancer

    • myc: lymphoma

    • abl: chromic myeloid leukemia or CML

Classification of Cancerous Tumors