Essay/Term paper: Tumours

Essay, term paper, research paper:  Biology

A tumour is a mass of new tissue
growth that does not react to normal controls or
the organizing influence of other tissues, and it has
no useful function in the body. This applies to both
types of tumours, malignant and benign. Malignant,
also known as, cancerous tumours, are
additionally defined by their invasion of local tissue
and their ability to spread to other parts of the
body. Benign Tumours A benign tumour which is
not cancerous, is less serious than malignant
tumours because they do not spread to other parts
of the body, but they may cause damage by local
growth and pressure on other structures,
producing serious complications such as bleeding.
Benign tumours generally grow slowly and kill the
host only if it occupies or attaches to an organ so
as to interfere with a critical function. The cells of
benign tumours closely resemble the cells of the
tissue of origin. Surface benign tumours include
warts and moles. Malignant Tumours A malignant
tumour always kills (unless treated) because of its
invasive and metastatic characteristics. The tumour
grows locally by spreading into surrounding
tissues. Solid tumours, which develop in the
breast, colon, lung, and other organs, contain an
inner core with high pressure zones that compress
and collapse blood vessels, often preventing the
penetration of blood- borne - 2 - cancer
treatments. It spreads to distant sites by the
breaking off of malignant cells, which move
through the blood and lymphatic systems, attach
themselves, and begin to grow as new colonies.
Malignant tumours are diagnosed by examination
of their vascularity, shapes, forms of cells division,
and differentiation. More than a hundred different
types have been identified in humans. In general,
those derived from epithelial tissue are
carcinomas, and those from connective tissue are
sarcomas. The most common form of malignant
tumour of the respiratory tract is lung cancer,
which began increasing in frequency at an alarming
rate about 1940. In 1980 it was the leading cause
of cancer deaths in men and is also rapidly
increasing in woman. It is attributed to cigarette
smoking and environmental pollution: cancer of the
lung is rare in nonsmokers, and exposure to
materials such as asbestos, chromium, and
radioactive substances increases the probability of
developing lung cancer. Malignant tumours, also
known as lymphomas, one of the main types of
lung cancer, arise in the lymph nodes related to the
lungs and other body tissue. the other main type of
lung cancer is Sarcomas, it may originate in the
lungs or in some other structure such as a bone.
Sarcomas have a poor prognosis, but recent
advances in the treatment of lymphomas have
increased the long term survival. The factors
controlling tumour growth are poorly understood,
although genetics seems to play a role Tumours in
- 3 - laboratory animals may be transplanted to a
second host using only a single tumour cell. This
suggests that only one normal cell needs to
become cancerous for tumour growth to begin.
Tumours have been experimentally induced in
animals by chemical, physical, and viral agents,
and by radiation. Cancer researchers no longer
believe that a single drug will be able to cure
cancer. Experts now believe that a combination of
drugs will be the best method to kill tumours. One
route being researched utilizes antibodies that bind
to specific receptors on the tumour cell, thereby
inhibiting tumour growth by blocking certain
tumour-growth factors from entering the cell.
Tumour necrosis factor (TFN), an immune-system
protein, has been found effective in cutting off the
blood supply to tumours, although too much TFN
causes severe side effects. The work of physician
Francis Peyton Rous, gave rise to the virus theory
of the causes of cancer. In 1960, Rous found that
he could transmit a cancerous tumour (sarcoma)
from one hen to another by using an injection of
tumour filtrate. The sarcoma virus was the first
tumour virus identified, and it opened up a whole
new area of cancer research. Rous shared the
1966 Nobel Prize for physiology or medicine for
his work.