Malignant Tumors of Oral Cavity and Oropharynx
Squamous cell carcinoma (SCC), an epidermoid cancer, is the most common malignancy in the oral cavity and oropharynx. It arises from the epithelial lining of the oral cavity in order of decreasing frequency in the lips, tongue, floor of the mouth, gingiva, and palate. In the oropharynx, it arises most often from the palatine tonsillar crypts. Although there are similarities in squamous cell carcinogenesis in the oral cavity and oropharynx, significant clinical and biologic differences also exist, suggesting that SCCs in the two regions are two separate disease entities. Both oral cavity and oropharyngeal cancers have a male predominance, and both are rarely seen before the age of 50. A striking difference between the two malignant processes is the declining incidence of SCC in the oral cavity and the rising incidence of it in the oropharynx. Tobacco is the most significant risk factor for the development of oral cavity SCC. Alcohol has a synergistic effect with tobacco as a carcinogen in this process. Betel nut chewing, radiation exposure, vitamin deficiencies, and environmental and occupational exposures are atypical risk factors in the development of SCC. Although tobacco remains a risk factor for the development of oropharyngeal cancer, human papillomavirus infection, specifically with serotype 16, is likely the most important causative agent in the development of SCC of the oropharynx.
Oral cavity cancer typically begins with a malignant precursor of leukoplakia or erythroplakia. In leukoplakic lesions, the tendency toward malignant growth is high if the cells of the prickle cell layer show disorientation with dyskeratosis. Fissuring and papillomatous formation are clinical danger signs during the transformation process of the premalignant lesion. In contrast, a precursor lesion is not typically seen with oropharyngeal SCC. Dysphagia, odynophagia, otalgia, and weight loss are clinical presentations shared by both oral and oropharyngeal SCC. Dentition problems and oral bleeding are typical of oral SCC, and obstructive sleep apnea and the presence of a neck mass are frequent findings in oropharyngeal SCC. The gross appearance of SCC varies from grayish white, nondescript, thickened mucosa consistent with its precursor leukoplakia to large flat, ulcerated lesions or bulky fungating masses with or without local invasion. Dysplastic epithelial changes occur early in the disease course. Basement membrane compromise is indicative of invasive disease, allowing for perineural and lymphovascular invasion. Histologically, most oral SCC lesions demonstrate squamous differentiation, with nests of cells with pink cytoplasm, intercellular bridges, and keratin pearls with a desmoplastic stroma. Oropharyngeal SCC demonstrates “blue cell” morphology with scant cytoplasm and hyperchromatic nuclei with high mitotic activity and little to no keratinization. Regional or cervical lymph node spread is frequently seen with oropharyngeal SCC and much less often with oral SCC. In tumors associated with human papillomavirus infection, the overall prognosis is much better for oropharyngeal SCC than for oral SCC. Treatment for both diseases includes a “cocktail” of irradiation and chemoirradiation and/or surgical resection.
Luetic glossitis, considered a premalignant lesion, is an oral manifestation of syphilis, which presents as diffuse lingual atrophy with a loss of papillae. Kaposi sarcoma is an endothelial malignancy seen in the oral cavity, primarily in patients with AIDS. Rarely, it can be found in older men of eastern European or Mediterranean descent; in patients from endemic areas of Africa, specifically Bantu children from South Africa; and in immunosuppressed individuals, particularly transplant recipients. The clinical subtypes differ according to the epidemiologic group affected. The most common site in the oral cavity is the palate, followed by the gingiva and dorsal surface of the tongue. The appearance of the lesion depends on the point in time that it is seen during the disease course. Early lesions are flat, red, and asymptomatic, and late lesions are larger, darker, and raised, with ultimate progression to large nodular lesions that ulcerate, bleed, and are painful. The incidence of this lesion has decreased dramatically with the widespread use of highly active antiretroviral therapy (HAART).
Lymphosarcoma, as well as other varieties of lympho- blastomas, may be observed occasionally in the oral cavity. The tumor originates from lymphoid tissue in the submucosa, especially the palate and pharynx. Typical features of this type of tumor are rapid growth and early local and regional lymph node metastases.