In cancer medicine, the term 'head and neck' has a particular meaning. The head and neck region includes the:

• mouth – made up of the lips and the structures inside the oral cavity such as the tongue, palate and gums
• throat – known as the pharynx
• voice box – known as the larynx
• nose – made up of the nasal cavity (the area behind the nose) and the sinuses
• salivary glands – in the floor of the mouth and near the lower jaw
• skin of the head and neck.

Other structures found in our head and neck are not considered part of the 'head and neck' in cancer medicine. Although they can be affected by nearby head and neck cancers and their treatment, and can also have their own types of cancer. These include the:

• brain
• eyes
• thyroid – a hormone-producing gland found at the front of the neck and just below the voice box
• oesophagus – the food pipe
• trachea – the windpipe
• bones and muscles of the head and neck.

The head and neck region also contains many lymph nodes, which are small, bean-shaped structures found throughout the body. They form part of the lymphatic system, which helps protect the body against disease and infection. When cancer spreads, it usually spreads to nearby lymph nodes first. 

Cancer that starts in the mouth is known as oral cancer. The mouth is made up of the lips and the oral cavity, which includes the:

• gums
• lining of the cheeks and lips
• front two-thirds of the tongue (oral or mobile tongue)
• floor of the mouth under the tongue
• bony roof of the mouth (hard palate)
• small area behind the wisdom teeth (retromolar trigone).

The area at the back of the mouth is called the oropharynx. It includes the base of the tongue, the tonsils, the uvula and the soft palate, as well as the middle section of the throat. Cancer of the oropharynx is known as oropharyngeal cancer.

Symptoms of mouth cancers include:

• mouth pain
• pain when swallowing
• a persistent sore or swelling in the mouth, or the area not healing after having a tooth extracted
• a sore throat that doesn’t get better
• unusual bleeding or numbness in the mouth
• red or white patches on the gums, tongue or mouth
• bad breath
• changes in speech or trouble pronouncing words
• difficulty chewing or swallowing food or moving the tongue
• weight loss
• loose teeth, or dentures that no longer fit
• earache.

The throat, also called the pharynx, is a hollow tube that starts behind the nose and leads to the food pipe (oesophagus) and the windpipe (trachea). The pharynx has three main parts:

• nasopharynx – the upper part, behind the nose and above the soft palate. Cancer starting in this area is called nasopharyngeal cancer.
• oropharynx – the middle part, the area from the soft palate and base of the tongue to the back of the mouth, including the tonsils. Cancer starting in this area is called oropharyngeal cancer.
• hypopharynx – the lower part, around the voice box (larynx). Cancer starting in this area is called hypopharyngeal cancer.

Cancers in the three parts of the pharynx are treated differently.

Symptoms of throat cancers include:

• a lump in the neck
• a persistent sore throat or cough
• difficulty swallowing or opening the mouth wide
• coughing up bloody mucus
• bad breath
• weight loss
• voice changes or hoarseness
• dull pain around the neck
• earache
• feeling that your air supply is blocked
• numb face
• a blocked nose
• hearing loss
• headache.

The voice box, also called the larynx, is the entry point to the windpipe (trachea). It contains the vocal cords and protects the lungs. Cancer that starts in the larynx is called laryngeal cancer. The larynx has three main parts:

• supraglottis – the area above the vocal cords. It includes the epiglottis, a small flap of tissue that covers the larynx when you swallow and prevents food and fluids going into the trachea and lungs.
• glottis – the area containing the vocal cords, which vibrate when air passes through them to produce the sound of your voice.
• subglottis – the area below the vocal cords leading to the trachea.

The thyroid gland is in front of the trachea under the voice box, but thyroid cancer is not considered head and neck cancer. 

Symptoms of voice box cancers include:

• a persistent change in the sound of your voice, including hoarseness
• a sore throat that doesn’t get better
• difficulty swallowing or pain when swallowing
• coughing all the time
• difficulty breathing
• weight loss
• pain in the ear.

The nasal cavity is the large, hollow space behind the nose. It is separated into two main cavities by the nasal septum, a thin wall of bone and cartilage in the centre of the nose.

The paranasal sinuses are small, air-filled spaces in the side walls of the nose. They help to warm and moisten air passing to the lungs. They also influence the sound and tone of your voice. There are four pairs of paranasal sinuses:

• maxillary sinuses – under the eyes and in the cheek area
• frontal sinuses – behind the forehead
• ethmoid sinuses – above the nose and between the eyes
• sphenoid sinuses – behind the nose and between the eyes.

Cancer that starts in the upper part of the throat behind the nose is called nasopharyngeal cancer.

Symptoms of nose cancers include:

• reduced sense of smell
• a persistent blocked nose or ear
• frequent nosebleeds
• lots of mucus in the throat or back of nose
• frequent headaches or sinus pressure
• difficulty swallowing
• loose or painful upper teeth
• a lump on or in the face, nose or mouth
• numb face, upper lip or inside mouth
• pressure or pain in ears
• a bulging or watery eye
• double vision or complete or partial loss of eyesight.

The salivary glands make the watery substance known as saliva. This keeps the mouth moist to help with swallowing and talking and also protects the mouth and teeth. There are three pairs of major salivary glands:

• parotid glands – in front of the ears
• submandibular glands – under the lower jaw
• sublingual glands – under the tongue.

There are also hundreds of smaller glands throughout the lining of the mouth, nose and throat. These are known as minor salivary glands. Cancers can start in the major or minor salivary glands. When cancer is found in one of the parotid glands, it has often spread from a skin cancer on the head or neck. 

Symptoms of salivary gland cancers include:

• swelling or a lump near the ear, jaw or lip, or inside the mouth
• left and right sides of the face or neck looking different (asymmetry)
• drooping, numbness or muscle weakness on one side of the face (palsy).

Cancer can start in the brain, eye, oesophagus, trachea and thyroid, or in bone or muscle of the head and neck. These cancers are not usually classified as head and neck cancers.

The first sign of cancer is often a lump under the skin of the neck or cheek. This can happen when cancer has spread to a lymph node. Your doctors will run tests to work out what type of cancer it is. It might be a head and neck cancer or it might be a cancer that has spread from elsewhere in the body (e.g. stomach cancer can spread to a lymph node in the neck and will still be considered stomach cancer).

Occasionally, tests show that a cancer in the head and neck started in another part of the body, but it is unclear where it started. This is called cancer of unknown primary (CUP).

Other risk factors account for only a small proportion of head and neck cancers. These include:

• having persistent sores or red or white patches in the mouth
• chewing tobacco, betel nut, areca nut, paan or gutka
• breathing in asbestos fibres, wood dust or certain chemicals
• poor dental health
• having a weakened immune system
• having had radiation therapy to the head or neck area in the past
• having too much sun exposure (for head and neck skin cancer)
• being overweight or obese
• having a parent, child or sibling with head and neck cancer (possibly because you have similar lifestyle factors)
• inheriting a condition linked to head and neck cancer (e.g. Fanconi anaemia, Li-Fraumeni syndrome).

Talk to your doctor if you are worried about any risk factors.