Cancer is a disease of the cells, which are the body’s basic building blocks. The body constantly makes new cells to help us grow, replace worn-out tissue and heal injuries. Normally, cells multiply and die in an orderly way.

Sometimes cells don’t grow, divide and die in the usual way. This may cause blood or lymph fluid in the body to become abnormal, or form a lump called a tumour. A tumour can be benign or malignant.

Benign tumour

Cells are confined to one area and are not able to spread to other parts of the body. This is not cancer.

Malignant tumour

This is made up of cancerous cells which have the ability to spread by travelling through the bloodstream or lymphatic system (lymph fluid).

The cancer that first develops in a tissue or organ is called the primary cancer. A malignant tumour is usually named after the organ or type of cell affected.

A malignant tumour that has not spread to other parts of the body is called localised cancer. A tumour may invade deeper into surrounding tissue (local invasion) and can grow its own blood vessels (angiogenesis).

If cancerous cells grow and form another tumour at a new site, it is called a secondary cancer or metastasis. A metastasis keeps the name of the original cancer. For example, oral cancer that has spread to the lungs is called metastatic oral cancer, even though the person may be experiencing symptoms caused by problems in the lungs.

The head and neck

The head and neck includes the following organs and body parts:

+ Mouth (oral cavity)

The mouth includes the lips, gums and tongue. The muscles of the base of the tongue (tongue base) continue into the upper throat (oropharynx).

The roof of the mouth is called the hard palate. Behind this is the soft palate. The soft palate lifts to close off the passageways to the nose so food does not go through the nose when swallowing.

Under the tongue and near the upper back teeth are salivary ducts that release saliva into the mouth. These are joined to salivary glands. The major glands are in front of the ears, and under the jaw and tongue. There are hundreds of minor glands in the mouth lining.

+ Throat (pharynx)

The pharynx is a tube that runs from the back of the nose to the gullet (oesophagus) and the windpipe (trachea). The pharynx has three parts: the nasopharynx, oropharynx (including the tonsils) and hypopharynx.

Air passes through the nasopharynx as you breathe in and out. Both food and air pass through the oropharynx and hypopharynx.

Food goes into the stomach via the oesophagus, while air goes into the trachea to get to the lungs.

+ Voice box (larynx)

The larynx is a short passageway that connects the lower part of the pharynx (hypopharynx) with the winwhen air passes through them to produce sound. Above the vocal folds is a small flap of tissue called the epiglottis, which prevents food going into the trachea when you swallow. Below the vocal folds is the subglottis.

Under the voice box, in front of the trachea, is the thyroid gland.

+ Nasal cavity and paranasal sinuses

The nasal cavity is the large, air-filled space behind the nose. The nose and upper respiratory tract warm, moisten and filter the air that you breathe.

Paranasal sinuses are air-filled spaces within your skull that help to lighten the weight of your head. They also produce mucus and vibrate sound when you speak or sing. The sinuses are in four locations: frontal, ethmoid, sphenoid and maxillary.