Oral cavity (Mouth) - The oral cavity includes the lips, the front two-thirds of the tongue, the gingiva (gums), the buccal mucosa (lining inside the cheeks and lips), the floor (bottom) of the mouth under the tongue, the hard palate (bony top of the mouth), and the small area behind the wisdom teeth.

Salivary glands - The salivary glands produce saliva, the fluid that keeps mucosal surfaces in the mouth and throat moist. There are many salivary glands; the major ones are in the floor of the mouth, and near the jawbone.

Paranasal sinuses and nasal cavity - The paranasal sinuses are small hollow spaces in the bones of the head surrounding the nose. The nasal cavity is the hollow space inside the nose.

Pharynx (Throat) - The pharynx is a hollow tube about 5 inches long that starts behind the nose and leads to the esophagus (the tube that goes to the stomach) and the trachea (the tube that goes to the lungs). The pharynx has three parts:

• Nasopharynx - The nasopharynx, the upper part of the pharynx, is behind the nose.
• Oropharynx - The oropharynx is the middle part of the pharynx. The oropharynx includes the soft palate (the back of the mouth), the base of the tongue, and the tonsils.
• Hypopharynx - The hypopharynx is the lower part of the pharynx.

Larynx - The larynx, also called the voicebox, is a short passageway formed by cartilage just below the pharynx in the neck. The larynx contains the vocal cords. It also has a small piece of tissue, called the epiglottis, which moves to cover the larynx to prevent food from entering the air passages.

Metastatic squamous neck cancer with unknown (occult) primary -Sometimes, squamous cancer cells are found in the lymph nodes of the upper neck when there is no evidence of cancer in other parts of the head and neck.

Thyroid - The thyroid is a gland at the base of the throat near the trachea (windpipe). It is shaped like a butterfly, with a right lobe and a left lobe. The isthmus, a thin piece of tissue, connects the two lobes. A healthy thyroid is a little larger than a quarter. It usually cannot be felt through the skin. The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones. Thyroid hormones do the following:

• Control heart rate, body temperature, and how quickly food is changed into energy (metabolism).
• Control the amount of calcium in the blood.