Risk Factors Associated With the Development of Oral Cancer
There are many factors associated with an increased risk of developing oral cancer. These include tobacco use, alcohol use, past history of oral-pharyngeal cancer, immunodeficiency, sun exposure, oral infection with human papilloma viruses 16 or 18, family history of first degree relatives with head and neck cancer, and advancing age. There are also synergistic effects among some of these factors.
Oral Cancer Examination
In conducting a visual exam of the oral cavity it is important to be familiar with the spectrum of normal findings so that deviations from normal (like discolorations or lesions) are readily appreciated. Frank squamous cell carcinomas are usually preceded by premalignant surface lesions. Premalignant lesions can be white (leukoplakia), red (erythroplakia), or a combination of white and red (erythroleukoplakia). Although oral mucosal leukoplakia is most often associated with premalignant changes, the red lesions are the ones most likely to demonstrate precancerous or early malignant changes. The latter lesions and red and white lesions carry the greatest risk of becoming carcinomas.
Oral malignant melanomas usually appear as pigmented lesions of the mucosa. Fortunately, these lesions are extremely rare. It is important to be aware of any newly identified and unexplained pigmented lesion or a pre-existing pigmented lesion that recently changed appearance. Certain benign processes can be mistaken for a melanoma. Among such processes are ethnic pigmentations, amalgam tattoos, and drug-induced pigmentations. The gingival and palate are the highest risk areas for intraoral melanoma.
Kaposi's sarcoma (KS) is the most common malignancy associated with acquired immune deficiency syndrome (AIDS). KS is an angioproliferative disease, representing both an inflammatory hyperplasia and a neoplastic process. The skin is the most common site for this cancer but in about half of those with this disease, an oral lesion is observed.
A complete inspection of the oral and oropharyngeal soft tissues and head and neck lymph nodes should be conducted at each dental hygiene exam appointment. An individual determined to be at risk for oral cancer may require a more frequent recall interval than caries or periodontal risks would dictate. It is important to ask the patient if they have noticed any lumps, bumps, bruises or sores that have not healed or experienced any problems with swallowing. Persistent sore throat, hoarseness, foreign body sensation in the throat and ear pain may also be signs of oropharyngeal cancer.
Components of an Oral Cancer Examination
A good oral examination requires an adequate light source, protective gloves, gauze squares, and a mouth mirror.
- Extraoral examination
- Inspect head and neck (including the back of the neck)
- Bimanually palpate lymph nodes and salivary glands
- Closely inspect the face (including the external ears) for skin lesions
- Inspect and palpate outer surfaces of lip and vermillion border
- Inspect and bidigitally palpate inner labial mucosa (upper and lower)
- Buccal mucosa
- Inspect and palpate inner cheek lining
- Alveolar ridge and gingiva
- Inspect maxillary/mandibular gingiva and alveolar ridges on both the buccal and lingual sides
- Have patient protrude tongue and inspect the dorsal surface
- Have patient lift tongue and inspect ventral surface
- Grasping tongue with a piece of gauze and gently pulling it out to each side, inspect the lateral borders of the tongue from its tip back to the lingual tonsil region posteriorly
- Palpate tongue
- Floor of mouth
- Inspect and palpate floor of mouth bimanually
- Hard palate
- Inspect and palpate hard palate
- Palpate for any lumps
- Soft palate and oropharynx
- Gently depress the patient's tongue with a mouth mirror, inspect the soft palate, tonsillar pillars, and oropharynx
Screening and Diagnostic Tools for Oral Cancer
Visual examination of the oral soft tissues, extraoral head and neck tissues and palpation of head and neck lymph nodes is considered the standard of care as part of a complete dental examination. The oral and oropharyngeal tissues lend themselves to visual inspection. One estimate suggests 5% to 10% of routine dental patients have some unusual findings in the oral cavity. Most such findings are benign and reactive in nature, but more rarely a more serious condition like squamous cell carcinoma is detected. A thorough and detailed visual exam along with palpation of tissues is the first step in identifying variations from normal and making an assessment of which conditions pose no threat from those that may lead to more serious consequences.
The biopsy is the gold standard for diagnosing oral cancers. A representative tissue sample obtained surgically and submitted for histopathological examination is the most definitive means of diagnosing oral cancer. A number of screening tools are either commercially available or in development or preparation for distribution. These products purportedly offer help in distinguishing which oral lesions should be biopsied. However, none of them can be relied on to establish definitive diagnoses.
Toluidine blue is a metachromatic dye that has been used for over 40 years to stain tissues suspected of being neoplastic. Toluidine blue stains mitochondrial deoxyribonucleic acid (DNA) and cells with greater than normal DNA or altered DNA. It has been found to be useful in selecting sites for biopsy.
ViziLite is a relatively new product developed for evaluating and monitoring oral mucosa abnormalities in populations at increased risk for oral cancer. Acetic acid is applied throughout the mouth and then the tissues are viewed using a special light. In some anatomic regions other than the oral cavity, precancerous lesions appear very opaque-white under this special light. This diagnostic technique has been used successfully in gynecology and is called a colposcopy. However, further study is needed to determine what role, if any, this test should play in screening for oral cancer. This product may be of benefit in following patients who have been diagnosed with dysplasia due to its relatively low rate of false negatives.
The brush "biopsy", an exfoliative cytologic technique was developed as a means of harvesting a transepithelial sample of cells from an oral surface lesion without having to anesthetize and remove an actual tissue sample (i.e., biopsy specimen) with the scalpel. This, too, is simply a screening tool similar to one that has been used in gynecology for a number of years and is known as a Papanicolaou ("Pap") smear. Many dysplastic lesions are first identified by histopathologically evident changes in the morphology of cells in the epithelial basal cell layer. Therefore, in order to be of use, the brush must obtain cells from this layer. This test can be used as a preliminary tool in helping to confirm a clinician's suspicion regarding an oral lesion. It must be emphasized that a brush "biopsy" sample analysis does not and cannot provide a definitive diagnosis for oral cancer. A tissue biopsy must be obtained to confirm the diagnosis.
Once a diagnosis of oral cancer has been made, imaging studies may be undertaken to determine the extent of the disease. Current imaging techniques include computed tomography (CT) scan, magnetic resonance imaging (MRI), and positron emission tomography (PET). Ultrasonography may also be useful.