Oral Cavity Anatomy and Function
Oral cavity has many different types of tissue located in this relatively small area. The oral cavity (mouth) begins at the lips and extends backwards to the front part of the tonsils. Beginning at the front of the upper and lower lips is the very specialized tissue called the vermilion border, which lines the lips. Once inside the mouth, this entire region is coated with a lining that is specialized to provide lubrication of the mouth. The bone of the lower jaw (mandible) and of the upper jaw (the hard palate), are also included in this region as well as the teeth. The lining of the mouth becomes thick overlying this bone. Directly behind the lower teeth is a smooth gutter, known as the floor of mouth. Here, the lower saliva gland empties saliva through specialized ducts just under the tip of the tongue. The front two-thirds of the tongue are also included within the oral cavity. The last part of the oral cavity, located in the rear of this region, is the retromolar trigone. This is a firm area just behind the back molars in the lower jaw.
The specialized lining of the mouth as well as the many saliva glands provide lubrication which aide in speech, swallowing and in the digestion of food. The grinding and crushing of food, which occurs in the oral cavity, is also important for digestion. Once foods are prepared for swallowing, the oral cavity helps in swallowing as the tongue and the mouth push the food backward towards the swallowing tube - the esophagus. Finally, our speech would not be possible without the structures of the oral cavity.
Incidence, Epidemiology and Pathology
Although cancers of the head and neck region only account for five percent of all cancers reported yearly in the human body, 30 percent of these cancers occur in the oral cavity. Cancers of the oral cavity left untreated can have devastating effects on critical life functions for people who have this disease. Similarly, choice of treatment must take into account the potential loss of function in this area. Cancers of the oral cavity may involve any single one of these specialized types of tissue or more than one. As noted, tissues in this area include bone, teeth, muscle, nerves, a rich supply of blood vessels, numerous saliva gland, and the specialized lining called mucosa. Although tumors may arise in any of these types of tissues they are most commonly related to changes in the lining of the mouth. The most common cancer of the oral cavity is called squamous cell carcinoma and arises from the lining of the oral cavity. Over 95 percent of oral cavity cancers are squamous cell carcinomas and these cancers are further subdivided by how closely they resemble normal lining cells: well differentiated, moderately differentiated and poorly differentiated. Other types of cancers of the oral cavity include cancers of the salivary glands such as mucoepidermoid carcinoma and adenoid cystic carcinoma, sarcomas (tumors arising from bone, cartilage, fat, fibrous tissue or muscle), and melanomas. The pathologist may also described characteristics of the tumor which make it more concerning such as: deep invasion of the tumor, invasion of nerves, invasion of the lymph vessels, invasion of blood vessels and the presence of multiple separate cancers in the area.
What are the risk factors for mouth cancer?
Tobacco and alcohol use are the major risk factors for most cancers of the head and neck including the oral cavity. Although the most common use of tobacco in the United States is cigarette smoking, the use of smokeless tobacco, or chew, is associated with oral cavity cancers. The most common site for oral cavity cancer in the United States is the tongue. In other regions of the world, different areas are more commonly affected. In countries such as India, where the use of a specific type of smokeless tobacco and a substance called beetle nut is common, the inner cheek area of the oral cavity is most commonly affected.
What are the symptoms and signs of mouth cancer?
The most common sign of mouth cancer is a non-healing wound on the tongue, in the floor of mouth or along the inner cheek. These can be painful, but in some cases do not cause significant discomfort. There may be on and off bleeding from the area. As the lesions increase in size, more symptoms occur. Complaints may include new or increased pain, pain was swallowing, ear pain, a change in speech, uncoordinated swallowing, or a lump in the neck. The most important factor to note is that sores in the mouth, whether they are related to trauma or to a variation of canker sores, should fully heal within three weeks. If this does not occur attention should be sought and trained professional should evaluate this region.
How is mouth cancer evaluated and diagnosed?
The Head and Neck Surgeon or - a thorough history will be taken asking for some of the symptoms noted above. Risk factors are sought including tobacco and alcohol use as well as the family history of cancer. A complete physical examination of the area is undertaken. Examination will usually be done of the entire head and neck region including the throat nose and ears. Particular attention will be given to feeling the neck to note if there are signs of cancer spread to lymph nodes in the neck called metastases.
A recommendation may be given to obtain a specialized type of X-ray, such as a CT scan or MRI. One or both of these can may be necessary. The physician may also order an X-ray or CT scan of the chest to see if there is any spread of disease to the lungs, the most common site of spread outside of the neck.
At this point, a biopsy – a small piece of tissue taken from the suspected tumor - is often taken in the office. The surgeon may also wish to do the biopsy with the patient under anesthesia. Evaluation of the entire throat, voice box, esophagus, and windpipe is also often recommended. This is done because between 5 to 15% of individuals who have one cancer of the mouth, throat or voice box may also have another tumor present elsewhere in the head and neck.
Tumor Staging
Once a full examination has been completed as well as the necessary X-rays and biopsies, the tumor is “staged.” Staging is a well-defined method of describing the exact extent of a specific tumor in an individual patient and then placing that tumor in a specific category. This not only assists in choosing treatment options, but also helps predict how successful therapy will be.
Treatment
The three main tools for treating cancers of the oral cavity are surgery, radiation therapy, and chemotherapy. For this reason, someone with a cancer of the oral cavity may also meet a specialist from radiation oncology as well as medical oncology. In general, Stage I and Stage II cancers require one type of treatment, either surgery or radiation therapy, to successfully control the cancer. Advanced Stage III and Stage IV cancers will often require combinations of surgery, radiation therapy and chemotherapy or even the use of all three.
Reconstruction
If surgery is required as part of the treatment of the cancer with in the oral cavity, a major emphasis is placed on providing successful reconstruction as needed. This reconstruction is intended to maintain function as well as appearance. Reconstruction may be as simple as putting the tongue muscles back together in the best possible fashion after the removal of the tongue cancer or the placement of a skin graft to replace the missing oral cavity lining. With more advanced cancers, more advanced reconstruction is required. In such cases, not only is new lining of the oral cavity needed in greater amount, but bone – such as the jawbone - may need to be replaced. In such cases, a surgeon may take tissues from elsewhere in the body. Skin and muscle can be moved from the chest to re-build the tongue and mouth. Skin can also be moved from the area of the wrist and used to reline the mouth and rebuild the tongue. Bone can be moved, with or without skin, from the lower leg, hip or shoulder blade and used to rebuild the upper or lower jaw.
Rehabilitation
Following the treatment of cancers in the oral cavity with surgery, radiation therapy chemotherapy or combinations of these, several important functions of the oral cavity may be severely affected. These include the lubrication of the mouth and throat, swallowing without choking on foods or liquids, speech and movement in areas where surgery has been done. Rehabilitation of various functions of the mouth may need to facilitated working with speech therapist.
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