The word cancer has its origin from Latin word Cancrum (Greek - Karakinos) which means crab. Various Types of tumours have also been described in Sushruta Samhita.
It is defined as in abnormal growth of cells in any tissue or organ of body. It has the tendency to spread and grow in other part of the body. The cancer cells preys on host cells and continue to grow indefinitely competing with normal cells for nutrition.
Most debatable question of 20th century is what causes cancer. After long period of confusion it is finally established that it is caused by mutation in both regulatory genes and tumour suppressor genes. Normal cell division (mitosis) in our body is highly regulated mechanism controlled by genes (made of DNA) through both regulatory pathways. A log exposure to carcinogens damage DNA and induce mutation in growth regulatory genes including oncogenes and tumour suppressor genes leading to loss of control over normal cell division. These mutated cells proliferate indiscriminately forming a mass called neoplasm or malignant tumour or in simple words cancer. With passage of time cancer cells further mutate.
More dangerous characteristics such as ability to invade and move into adjoining tissue flow through lymph and blood vessels lodge and grow into other parts of the body. And form colonies this process is called metastasis. Cancer cells can even create their own blood vessel (tumour angiogenesis) for their nutrition and become immortal by gaining ability of limitless replication.
By the time cancer is detected they have already added many Mutations.
Further exposure to radiations of X-Rays, C .T Scans, PET Scans, Bone Scan etc. During investigations may induce more mutation making cancer cells more aggressive similarly radiotherapy chemotherapy hormonal therapy etc. Also induce mutation making them resistant to therapy.
Risk of cancer increases when person is exposed to certain physical, chemical or biological agents collectively called carcinogenes by causing mutation in genes . Detoxifying enigmas protect us from cancer. If detoxification is slow carcinogenes accumulate reducing cancer.
Immune cells also protect from cancer by scavenging and destroying it. Most of newly formed cancer cells never grow beyond microscopic stage because immune system destroy it. This is done by t-lymphocytes, natural killers. Lymphoid activated killer(LAK) and macro phages.
Types of Cancer
Since there are many types of cells in the body hence different types of cancer
- Carcinoma - these cancers arise from epithelial cells these form 80% all human cancers example squamous cell carcinoma, basal cells carcinoma, glandular cells carcinoma,
- Sarcoma - these arise from connective tissues i.e. bone, cartridge, muscle, fatty tissue, fibrous tissue
- Myeloma - these arise from plasma cells
- Leukaemia these cancers arise from blood forming cells
- Lymphoma these arise from lymphatic tissue
- Tumours of CNS are named according to the cells example cancer of glial cells is called glioma
Spread of Cancer
Cancer spreads by two methods
Metastases - Cancer cells grow in size by infiltration and invasion destroying adjacent cells. After initial growth some cancer cells become free from primary tumour and penetrate into blood vessels and lymph channels and migrate to different tissues.
Other method is by implantation seeding. It occurs in organs with close contact to tumour.
Cancer staging system most common and globally accepted staging system is TNM classification
T - describe size or number of tumours
N - involvement of regional ling frauds
M - status of metastasis.
Property of Cancer
- Colonality - multiply two form clones
- Autonomy - not regulated by body
- An aplasia - do not have cellular differentiation
- Metastasis - can grow in other tissues and organs
Traits of human cancer
- Pathological mitosis - by activation of onco genes (rat and mice)
- Inactivation of tumour suppresser Genes -
- Evasion of prolonged cell death apoptosis
- Acquire proactive and limitless replication
- Tumour angiogenesis