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The advantages of CT include its rapid acquisition time seconds per section , patient tolerance, relatively low cost, and superior osseous detail compared with MRI. However, the soft-tissue contrast resolution of CT is relatively poor, which makes it difficult to distinguish between tumor and normal muscle. CT also may require the administration of intravenous contrast material to differentiate vessels from lymph nodes, thereby increasing the risk of an allergic reaction. In addition, CT is frequently degraded by scattered artifacts because of metallic dental appliances.
The superior soft-tissue resolution of MRI allows high-contrast differentiation between neoplasms and adjacent muscle. In addition, MRI can be obtained in multiple planes sagittal, axial, coronal, and oblique , which is often helpful in assessing tumor volumes during and after therapy. However, MRI is not without its drawbacks. Because all the images within a given MRI sequence are obtained simultaneously rather than sequentially, patient movement during an MRI is less well tolerated than with CT.
In addition, although the soft-tissue contrast is superb with MRI, fine-bone detail is inferior to that obtained with CT. Under certain conditions, exfoliative cytology cell scrapings serves as an adjunct to clinical diagnosis, as it enables more extensive screening and provides microscopic material if there is a delay in or contraindication to biopsy. However, cytologic smears are used infrequently, and patients are not treated on the basis of cytologic findings alone.
Smears are most helpful in differentiating inflammatory conditions, especially candidiasis, from dysplastic or neoplastic surface lesions. In addition, cytology may be helpful in detecting field change in oral cancer, especially if this method is used in conjunction with vital staining.
Cytology may also be helpful when ulcerations following radiation are suspicious and biopsy is delayed. Fine needle aspiration biopsy of subsurface masses is also an accepted diagnostic test, one that has increased in popularity over the past few years.
This technique is extremely useful in evaluating clinically suspicious changes involving salivary glands and lymph nodes. It expedites diagnosis and. When used by a skilled clinician, fine needle aspiration can often be the best way to establish a definitive diagnosis of unexplained masses of the neck or salivary glands.
It is also valuable in following up cancer patients with suspicious enlargements. The stage of the disease depends on several factors, including the size of the primary lesion, local extension, lymph node involvement, and evidence of distant metastasis.
This system has 3 basic clinical features: N2 Metastasis in a single ipsilateral lymph node, more than 3 cm but not more than 6 cm in greatest dimension; in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension; in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension.
N2a Metastasis in single ipsilateral lymph node more than 3 cm but not more than 6 cm in greatest dimension. N2c Metastasis in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension. M1 Distant metastasis The individual clinical parameters in the TNM classification system are grouped to determine the appropriate disease stage Table 5 ; stages are ranked numerically from 0 which has the best prognosis to IV the worst prognosis.
In general, oral staging classifications do not use histopathologic findings except to determine the definitive diagnosis. Schematic drawings of the tumor tumor maps are frequently prepared to document the site and size of the tumor at the initial time of diagnosis. This initial documentation is later complemented by histopathologic findings and imaging preformed during the treatment phase. Although the risk of distant metastasis is generally low in patients with oral cancer, there is a 17 correlation between the incidence of distant metastasis and tumor T and neck N stage.
When they do occur, the most frequently involved organs are the lungs, bone, and liver. Patients with advanced T or N stages may be at risk for developing metastases outside the head and neck region; a limited workup chest x-ray, CBC and liver function tests, bone scan to exclude such a metastasis may be indicated.
After completion of the initial workup, the final T, N, M metastasis , and overall stage assignment should be formally determined and documented prior to treatment. Oral squamous cell carcinoma spreads primarily by local extension and somewhat less often by the lymphatics. The lymphatic system is the most important and frequent route of metastasis. Usually the ipsilateral cervical lymph nodes are the primary site for metastatic deposits, but occasionally contralateral or bilateral metastatic deposits are detected.
The risk for lymphatic spread is greater for posterior lesions of the oral cavity, possibly because of delayed diagnosis or increased lymphatic drainage at those sites, or both. Cervical lymph nodes with metastatic deposits are firm-to-hard, nontender enlargements.
Once the tumor cells perforate the nodal capsule and invade the surrounding tissue, these lymph nodes become fixed and non mobile. Metastatic spread of tumor deposits from oral carcinoma usually occurs in an orderly pattern, beginning with the uppermost lymph nodes and spreading down the cervical chain.
Because of this pattern of spread, the jugulo-digastric nodes are most prone to early metastasis. Carcinomas involving the lower lip and floor of the mouth are an exception, as they tend to spread to the submental nodes.
Hematogenous spread of tumor cells is infrequent in the oral cavity but may occur because of direct vascular invasion or seeding from surgical manipulation.
Among the most common sites for distant metastasis are the lungs, liver, and bones. These patients cannot be cured and are treated with palliative intent, usually involving chemotherapy, radiotherapy, or both. These patients are treated with curative intent, usually involving surgery, radiation therapy, 2 or both. Tumor recurrences most often occur during the first 2 years after therapy; later recurrences are rare.
Thus, with sufficient follow-up time, second malignancies or other medical diseases become greater problems than recurrence of the primary disease. The use of drug therapy to decrease the rate of second malignancies is being actively investigated. Patients with locoregionally advanced disease T 3 , T 4 , N 1 , N 2 3 , and N are also treated with curative intent.
Given the advanced stage of their disease, surgery and radiation are utilized unless patients are considered inoperable or have unresectable disease. Despite this aggressive bimodality therapy, the majority of these cancers will recur within the first 2 years of follow-up, most commonly either locally or regionally. Some of these patients may have metastases outside the head and neck area, events that might be predicted by their initial T and N stages.
Investigational therapy in this group of patients, therefore, must focus primarily on delivering more effective locoregional care. However, should locoregional control be improved, chemopreventive strategies will need to be pursued in this group of patients as well since, in principle, oral cancer patients are at risk for developing second primary malignancies in the oral cavity, pharynx, and respiratory and digestive tracts. When a second malignancy occurs at the same time as the initial lesion, it is called a synchronous carcinoma.
Metachronous neoplasms, on the other hand, are additional primary surface epithelial malignancies that develop in a later time period than the original tumor. The remaining multiple cancers in this population represent metachronous disease and usually develop within 3 years 19 of the initial tumor.
The overall risk for developing a second head and neck malignancy is 10 to 30 times higher in populations that use tobacco and alcohol than in the general population. At the present time, the most effective approach to reducing morbidity and mortality from oral cancer is early detection. However, progress in this area requires changes in public and professional knowledge, attitudes, behaviors, and practices see Chapter IX for a full discussion.
The use of immunohistochemical techniques to establish a definitive diagnosis has expanded during the past decade and continues to be refined.
These diagnostic tests help to establish a definitive diagnosis when, by routine histopathology techniques, a lesion appears morphologically benign or its classification is in doubt. Research on the biochemical, genetic, and cellular levels should yield information that will identify high-risk groups for many types of cancer including oral cancer. Imaging techniques continue to improve at a rapid rate. Newer imaging techniques hold promise for 24 clinical staging of T 2, T 3 and T 4 1 lesions, but T lesions are typically too small to be visualized.
Improvements that increase definition will promote earlier detection of nasopharyngeal, submucosal, and bone lesions. One such technique appropriate for lymph nodes is positron emission tomography, which may help to define tumor activity in clinically negative areas. No matter which diagnostic technique is used, there is the possibility of a false-negative diagnosis. However, studies are under way to identify key markers that should improve accuracy.
The development of monoclonal antibodies that have high sensitivity and specificity for epithelial dysplastic and malignant cells would enhance accuracy of diagnosis in some cases where the usual or typical cellular characteristics of precancer or cancer are not apparent.
In addition, assuming that an antibody was specific for a particular cellular tumor antigen, binding of cytotoxic chemotherapeutic agents for killing tumors and sparing normal cells would be a logical and possibly feasible follow-up to surgery and radiation therapy to improve cancer control.
Additional knowledge about various cell markers that reflect growth and suppressor protein presence or activity may also prove to be of great value in predicting cell behavior. Current research is exploring the genetics of biochemical processes that may affect the development of oral cancer. Included are gene mutations such as tumor suppressor gene amplification and overexpression of proto-oncogenes c-myc, EGFR and cyclin D1, as well as loss of heterozygosity of specific chromosome loci.
Photodynamic therapy, also known as PDT, and photodetection of cancer may be useful in the oral cavity. Two important variables that must be considered are the uptake of the dye and the dye contrast by normal and neoplastic tissue after injection. The role that health care professionals who are not physicians or dentists play in oral cancer screening is poorly defined. The medical and dental professions need additional information on the most effective ways to provide early detection screening for all patients, including medically underserved populations.
In addition, health care professionals need to know how to instruct patients on oral self-examination techniques. Most practitioners are aware that such instruction is reasonable and practical for breast cancer but are unaware of its role in the early detection of oral cancer. Similarly, most of the general public is poorly informed about the risk of oral cancer and ways to prevent this disease. Much public attention is paid to the dangers of cigarette smoking, where the major emphasis is on lung cancer and cardiovascular disease, less on increased cancer risk in the upper airways and oral cavity.
In recent years more information has been directed toward oral cancer risks in smokeless tobacco abusers than in cigarette smokers. Most people have little interest in estimating their oral cancer risk based on age, sex, race, or even habits such as drinking or smoking. The portion of the public that regularly receives medical and dental care tends to assume it is routinely and adequately screened for all types of disease, including all forms of cancer.
These people are generally unaware that to screen properly for oral cancer requires a head, neck, and oral examination. Thus, the failure of a primary care doctor to perform those procedures would likely go unnoticed by the average patient. Similarly, many patients are no doubt unclear as to who should be responsible for screening them for oral cancer.
Although members of the public have been informed to some degree regarding the general warning signs of cancer, they may not know the early signs of oral cancer. Not surprisingly, far too many oral cancer patients do not seek care until their tumors are advanced, which suggests that a much better job must be done of informing patients when and how to seek help.
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