Principles Of Cancer

Diksha Bhatla

Principles Of Cancer

22 Jun 2022

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Introduction

When cells in some area of body duplicate without control, the excess of tissue that develops called tumor or neoplasm. The growth of neoplastic cells exceeds and is not co-ordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the stimuli. Tumors may be cancerous and sometime fatal or they may be quite harmless. A cancerous growth is called as malignant tumor or malignancy and noncancerous growth is called as benign growth. The study of tumor is called oncology. With the exception rare cases, cancer may be caused by inherited genetic defects and certain viruses. Specific cause is unknown. Several risk factors are associated with development of cancer.

All types of cancers are common, in that, the cancer cells are abnormal and multiply out of control. However, there are often great differences between different types of cancer. For example:

• Some grow and spread more quickly than others.

•Some are easier to treat than others, particularly if diagnosed at an early stage.

•Some respond much better than others to chemotherapy, radiotherapy, or other treatments.

• Some have a better outlook (prognosis) than others. For some types of cancer there is a very good chance of being cured. For some types of cancer the outlook is poor.
The incidence of cancer and cancer types are influenced by many factors such as age, sex, race, local environmental factors, diet, and genetics.

Classification of Cancer by Site of Origin

By primary site of origin, cancers may be of specific types like

•Breast cancer

•Lung cancer

•Prostate cancer

•Liver cancer

•Renal cell carcinoma (kidney cancer),

•Oral cancer

•Brain cancer etc.

Classification by Tissue Types

Based on tissue types cancers may be classified into six major categories:

1. Carcinoma: This type of cancer originates from the epithelial layer of cells that form the lining of external parts of the body or the internal linings of organs within the body.

Carcinomas, malignancies of epithelial tissue, account for 80 to 90 % of all cancer cases since epithelial tissues are most abundantly found in the body from being present in the skin to the covering and lining of organs and internal passageways, such as the gastrointestinal tract.

2. Sarcoma: These cancers originate in connective and supportive tissues including muscles, bones, cartilage and fat. Bone cancer is one of the sarcomas termed as osteosarcoma. It affects the young most commonly. Sarcomas appear like the tissue in which they grow.

3. Myeloma: These originate in the plasma cells of bone marrow. Plasma cells are capable of producing various antibodies in response to infections. Myeloma is a type of blood cancer.

4. Leukemia: This group of cancers are grouped within blood cancers. These cancers affect the bone marrow which is the site for blood cell production. When cancerous, the bone marrow begins to produce excessive immature white blood cells that fail to perform their usual actions and the patient is often prone to infection.

5. Lymphoma: These are cancers of the lymphatic system. Unlike the leukemias, which affect the blood and are called “liquid cancers”, lymphomas are “solid cancers”. These may affect lymph nodes at specific sites like the stomach, brain, intestines etc. These lymphomas are referred to as extra nodal lymphomas.

6. Mixed types: These have two or more components of the cancer. Some of the examples include mixed mesodermal tumour , carcinosarcoma, adenosquamous carcinoma and teratocarcinoma. Blastomas are another type that involves embryonic tissues.

Classification of Cancer by Grade

Cancers can also be classified according to grade. The abnormality of the cells with respect to surrounding normal tissues determines the grade of the cancer. Increasing abnormality increases the grade, from 1–4. Cells that are well differentiated closely resemble normal specialised cells and belong to low grade tumors. Cells that are undifferentiated are highly abnormal with respect to surrounding tissues. These are high grade tumours.

Grade 1: Well differentiated cells with slight abnormality.

Grade 2: Cells are moderately differentiated and slightly more abnormal.

Grade 3: Cells are poorly differentiated and very abnormal.

Grade 4: Cells are immature and primitive and undifferentiated.

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