Book 4 - Self Instructional Manual for Cancer Registrars - SEER ...

• Gums (gingiva). The gums are folds of mucosa which surround the base of the teeth. Thelamina propria is firmly attached to the underlying bone thus forming a fusion of mucous membraneand periosteum called "mucoperiosteum."The lower gum is the mucosa covering the alveolar process of the mandible. It extends from theline of attachment of mucosa in the buccal gutter (sulcus) on the outer margin to the line of freemucosa of the floor of the mouth on the inner side. Posteriorly it extends to the ascending ramusof the mandible (retromolar trigone).The upper gum is the mucosa covering the alveolar process of the maxilla. It extends from theline of attachment of mucosa in the gingival buccal sulcus to the junction with the mucosa of thehard palate. Its posterior margin is the upper end of the palatoglossal (pterygopalatine) arch.MalignantTumorsCancer occurs more frequently on the lower than on the upper gingiva. It will sometimes invadeunderlying bone, but can be distinguished from tumors originating in bone on the basis of thehistology. Malignant tumors of the gingival mucosa are almost always squamous cell carcinoma. Arare odontogenic tumor (ameloblastoma, adamantinoma) originating in the tissues which form theteeth may arise in the bone underlying the gingival mucosa.Figure 25.GINGIVASiiub co taoeo us tissueulc]L•.............. :,.x: t t,,Labia I mucosa---_ _...._iG£nlllsr&:178