What is the difference between malignant and benign tumours and how are they treated?

Richard Rees Page 01/05/2007

What is the difference between malignant and benign tumours and how are they treated?

To start with let us look at the definitions of the words:

Malignant: in mod. use applied to carcinoma and sarcoma, forming a class ‘characterized by their rapidity of growth, by the extension to the lymphatic glands, and by their recurrence in situ and in distant organs after removal’

Of diseases: Of a mild type; not malignant.

In a human cancer the progression goes like this. There is the normal mucosa. This is the state that of a healthy cell. That then becomes a precursor lesion. This is a benign tumour, normally unnoticeable and of no affect to the patient. A cancer probably spends most of its ‘life’ in this stage. It presents no symptoms and does not noticeably affect the routine function of the body. Then it becomes a dyplasia. This means that the cells have denatured and are the wrong type of cells in the wrong place. It starts to become noticeable at this stage, although still not malignant at all. Once the tumour becomes a carcinoma in situ, the patient is at risk, because the cancer may very quickly become an invasive cancer.

There are many types of cancer. A carcinoma is a malignant tumour of the epithelium.
        Sarcoma is a malignant tumour of mesenchymal cells. It can be thought of as malignant uncontrolled proliferation of connective tissue and muscle cells. These cells are mesenchymal in origin
        Teratoma is a tumour arising from multi-potential embryonic cells and composed of endoderm and ectoderm and mesoderm.
        Adeno or Squamus tumours have a glandular component.

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However all types of malignant tumours spread. There are four basic types of metastases. Local growth is where the cancer has direct involvement into surrounding tissue. Cancers can spread to completely different and random areas of the body by implantation. This is where metastases (little seedlings of cancer cells) are deposited in the lymph nodes or blood stream. These then travel around the system and get deposited randomly.

Once a tumour reaches a certain size the blood vessels that normally service the mucosa are inadequate and the tumour goes into angiogenesis. This is where the tumour develops a blood supply of its own.

How is it treated?

The treatment programme can only be set in motion once the patient presents to a doctor. However by this stage the tumour can be very advanced. Let us take for instance a patient who presents with all the symptoms associated with lung cancer. The GP (or in more serious cases the A&E doctor) then refers the patient to the chest physician who does a more thorough examination, probably including a chest x-ray etc. He will then make a diagnosis.

Then this gets presented to a multi-disiplinary team, consisting of GP, Macmillan nurse, surgeons, medical oncologists, chemical oncologists, and palliative care physicians. They will discuss the diagnosis and come to an agreement over the treatment. This may include, surgery radio- and chemo- therapy, hormone therapy or immunotherapy or a combination of the above. In addition the palliative care team will make sure that the patient can carry on with a normal life if possible, with the aim of keeping the patient at home, or in friendly surroundings as soon as possible.

There is another method of treatment that is being researched at the moment, although presently it is not very well understood even by the leading scientists. This is RNA interference. The theory is that if the cell can stop the genes that code for cancer (such as BRCA -1 the main breast cancer gene) functioning then the symptoms will never present effectively curing the patient. This would also work for viruses such as HIV foot and mouth or HPVs which are thought to lead directly to cervical cancer.

Oxford English dictionary (2nd ed.)