eRadiograph Volume 7: Imaging of Oral Cavity | Page 18

Floor of mouth cancer Floor of mouth cancers constitute 18% of all oral cavity squamous cell carcinomas. They may extend superiorly to involve the ventral tongue inferiorly through mylohyoid muscle into submandibular space, posteriorly into base of the tongue anterior/antero laterally into mandible. Lesions in the anterior floor of mouth may obstruct whartons duct and resultant dilatation of the duct and enlargement of submandibular gland or sialadenitis. Infact, floor of mouth lesions may be very small and easily missed but come to attention due to involvement of whartons duct. Most floor of mouth cancers arise in the anterior 2 cm, the neuromuscular bundle runs very close to the midline, extension across the midline to involve both near vascular bundles will necessitate a total glossectomy. Involvement of mandibular cortex, extrinsic muscles of tongue, skin of face, masticator space, ptyergoid or skull base constitute stage 4 disease. There may be lymphatic dissemination to sub mental, sub mandibular and periparotid adenopathy. RMT cancers constitute 7-12% of oral cavity cancers. They may extend anteriorly to the buccal mucosa, gingiva, posteriorly to anterior tonsillar pillar, soft palate, posterolaterally to masticator space. Hard Palate This is a thin horizontal bone which spans the arch formed by the palatine process of the maxilla and horizontal plates of palatine bone. The arch is formed by the alveolar ridges and upper teath. Posteriorly the hard palate is contigous with the soft palate. The junction between hard palate and soft palate is also the junction between the oral cavity and the oropharynx. It forms the roof of the oral cavity and the floor of the nasal cavity. The greater palatine nerve runs through the greater palatine foramen, which is located medial to the posterior third molar. This is a potential site of spread of tumor along the branches of V2 into the ptyergopalatine fossa.The hard palate is well depicted as a hypointense cortex and central hyperintense marrow. The hard palate is rich in minor salivary glands. These may be seen along the inferior surface of hard palate as enhancing foci. This is the reason minor salivary gland tumors are more common in the hard palate than squamous cell carcinoma, which predominates in the rest of the oral cavity. Adenocystic carcinoma, mucoepi dermoid carcinoma or adenocarcinoma may occur. These tumors may invade the maxillary sinus, palatine 18 Imaging of Oral Cavity Alveolar Ridge Cancers Upper alveolar ridge cancers may spread medially to the palate, maxillary sinus and nasal cavity. Lower alveolar ridge cancers may extend medially to floor of mouth, laterally to buccal space, masticator space. Since alveolar ridge cancers are close to bone - bony involvement is common as well as perineurial spread alongwith inferior alveolar nerve.