What are the Causes, Signs and Symptoms of Cancer?

Causes of Cancer:

Cancer is caused as a result of environmental factors and genetic factors.

Cancer is mostly due to environmental carcinogens but genetic factors may also be the reason in certain cases.

The environmental factors like consumption of tobacco, poor diet, obesity, radiation, infection, lack of physical activity and environmental pollutants alter the genetic material of the cells.

Cell reproduction is a complex process, regulated by several classes of genes like oncogenes and tumor suppressor genes. Alteration in these regulator genes leads to the development of cancer. These may be hereditary or acquired abnormalities. Few cancers are mainly hereditary.

What are carcinogens that cause mutation of DNA?

Carcinogens are the agents which can induce the formation of cancer. The agents may be physical, chemical or biologic agents and are capable of inducing cancer. These agents can damage the cellular DNA, either directly or by producing toxic intermediates such as free radicals. Certain viruses also act as oncogens. These viruses induce mutations in the host cell DNA or they may alter the rates of cellular transcription. Mutations of cellular DNA leads to the formation of cells with abnormal growth and differentiation characteristics.

List of Carcinogens:

Chemicals – Many chemicals like vinyl chloride, benzene, cigarette smoke, aromatic hydrocarbons etc.,

Radiation, radon gas, radioactive materials, ultraviolet radiation

Occupational exposure to certain metals in the industries – Asbestos, coal dust, uranium, solvents

Oncogenic viruses

Dietary factors– high fat diet, excessive intake of alcohol, nitrosamine preservatives, grilled or charred foods

Hormones – estrogens, progesterone

Oncogenic viruses in humans

Both the DNA and RNA viruses are found to be oncogenic in nature, which are capable of producing cancer in human hosts, they infect.

• Human Papillomavirus cause cervical carcinoma
• Hepatitis B virus cause liver cancer
• Epstein-Barr virus cause Burkitt’s lymphoma and nasopharyngeal cancer
• HIV virus cause Kaposi’s sarcoma

Hereditary factors:

Some cancers like colon cancer, breast cancer, retinoblastoma, leukemia and lymphoma are predisposed genetically. The present research is focused to identify certain genetic markers in individuals that are basis for development of certain types of cancer.

Signs and Symptoms of Cancer:

The symptoms of cancer can be classified into three groups like local symptoms, metastatic symptoms and systemic symptoms.

Local Symptoms: Local symptoms include

• Lumps
• Swelling
• Hemorrhage from mouth, anus or skin
• Ulceration
• Pain

The local symptoms are restricted to the site of the primary cancer. The initial swelling will be painless and local pain can be felt in the case of advanced cancer mainly.

Metastatic Symptoms: These symptoms occur as a result of spreading of cancer to other sites in the body.

The symptoms includes the enlargement of the organs

• Enlargement of the lymph nodes
• Hepatomegaly (enlargement of the liver; hepato=liver,megaly=enlargement)
• Splenomegaly (enlargement of the spleen)
• Pain
• Fracture of bones
• Neurological symptoms

The enlargement can be felt in the abdomen.

Systemic Symptoms: The symptoms include

• Weight loss
• Poor appetite
• Cachexia
• Fatigue
• Excessive sweating
• Anemia
• Paraneoplastic phenomena

These symptoms are not directly related to the metastatic spread or direct effects of the cancer. These are mediated by the immunological or hormonal signals from the cancer cells.

All the above symptoms are non-specific symptoms. They can be diagnosed. Patients who do not have cancer may also feel these kinds of symptoms.

Summary of clinical signs and symptoms and treatment

The presence of cancer cannot be suspected in the early stages, it can be detected only after medical imaging. Diagnosis of cancer requires microscopical examination of a biopsy specimen.

Cancer can be treated by methods like chemotherapy, radiotherapy and surgery.

The treatment depends on the type of tumor and stage of its development.

Chemotherapy can be used alone or in combination with other methods of treatment.