Cancers arising in the retromolar trigone (the narrow band of mucosa that lies behind the mandibular molars and covers the ascending ramus) are rarely confined to that gingiva, but involve adjacent buccal mucosa, anterior tonsillar pillar, the floor of the mouth, and/or posterior gingiva. Thus, retromolar trigone cancers that involve the anterior tonsillar pillar behave more like oropharyngeal cancers than like oral cavity primaries. The risk of clinically positive and occult lymph node metastases is higher than with other gingival cancers. The frequent involvement of periosteum mandates partial (rim or marginal) mandibulectomy as part of the surgical management, even for small lesions.

Primary radiation therapy is reserved for superficial lesions that cover a large surface area, such as extension to the soft palate or buccal mucosa, and remain mobile. Moderately advanced or deeply invasive lesions are best treated with surgical resection (mandibulectomy and neck dissection), followed by radiation therapy if indicated.

Oropharynx
The clinical staging of oropharyngeal cancers depends primarily on tumor size and is similar to the staging of oral cavity cancers (

Table 90-8). Although tumors may arise from any site in the oropharynx, they arise most commonly from the palatine arch, which includes the tonsillar fossa and base of the tongue. The most common presenting symptom is chronic sore throat (often unilateral) and referred otalgia.

Change in voice, dysphagia, and trismus are late signs. Regional lymphatic metastases occur frequently and are related to the depth of tumor invasion and tumor size. Upper cervical nodes are generally first involved, but lower nodes can become clinically involved with skipping of the upper first-echelon nodes. Bilateral lymphatic metastases can occur, particularly with cancers of the soft palate, tongue base, and midline pharyngeal wall.