Palatal & Mandibular Torus, & Exostosis

Palatal & Mandibular Torus, & Exostosis

While not technically soft tissue masses, the torus palatinus, torus mandibularis and bony exostosis (buccal exostosis) are all lesions which present as surface masses and are removed with minimal disturbance of deeper cancellous bones. As such, they are submitted to the pathologist as palatal or alveolar masses and might be confused with peripheral ossifying fibroma or other bone-producing soft tissue masses of the oral mucosa. For this reason, it is included in the present section.

The torus is considered to be a developmental anomaly, although it does not present until adult life and often will continue to grow slowly throughout life. It may be the outcome of mild, chronic periosteal ischemia secondary to mild nasal septum pressures (palatal torus) or the torquing action of the arch of the mandible (mandibular torus) or lateral pressures from the roots of the underlying teeth (buccal exostosis), but this is largely speculation. The most similar bony growth outside the jaws is the bunion of the lateral foot, and the earliest dental journal report of a torus palatinus was probably in an 1857 essay by Parmentier relating to tumors of the palate. The prevalence rate for tori is 27/1,000 adults (Table 1).

Clinical Features: These entities are all very site-specific. The palatal torus is found only in the midline of the hard palate (Figures 1 & 2). The mandibular torus is found only on the lingual surface of the mandible, near the bicuspid teeth (Figures 3 & 4). The buccal exostosis is found only on the facial surface of the alveolar bone, usually the maxillary alveolus.7 Bony surface proliferations found in another site are typically given the generic diagnosis of bony exostosis or osteoma, i.e. are considered to be trauma-induced inflammatory periosteal reactions or true neoplasms. Unless such a bony prominence is specifically located, is pedunculated or is associated with an osteoma-producing syndrome such as the Gardner syndrome, there may be no means by which to differentiate an exostosis from an osteoma, even under the microscope.

As previously stated, these lesions are not present until the late teen and early adult years, and many, if not most, continue to slowly enlarge over time. Fewer than 3% occur in children. Taken as a group, these lesions are found in at least 3% of adults and are more common in females than in males. The torus may be bosselated or multilobulated but the exostosis is typically a single, broad-based, smooth-surfaced mass, perhaps with a central sharp, pointed projection of bone producing tenderness immediately beneath the surface mucosa. Lesions may become 3-4 cm. in greatest diameter, but are usually less than 1.5 cm. at biopsy. A definite hereditary basis, usually autosomal dominant, has been established for some cases of tori and Asians, especially Koreans, have a much higher prevalence rate than do other racial groups.

Pathology: On cut surface the torus and exostosis show dense bone with a lamellar or laminated pattern (Figure 5). They are usually comprised of dense, mature, lamellar bone with scattered osteocytes and small marrow spaces filled with fatty marrow or a loose fibrovascular stroma. Some lesions have a thin rim of cortical bone overlying inactive cancellous bone with considerable fatty or hematopoietic marrow present. Minimal osteoblastic activity is usually seen, but occasional lesions will show abundant periosteal activity. Large areas of bone may show enlarged lacunae with missing or pyknotic osteocytes (Figure 6), indicative of ischemic damage to the bone. Ischemic changes such as marrow fibrosis and dilated veins may also be found in the marrow, with rare examples showing actual infarction of fatty marrow.

Treatment & Prognosis: Neither the torus nor the bony exostosis requires treatment unless it becomes so large that it interferes with function, interferes with denture placement, or suffers from recurring traumatic surface ulceration (usually from sharp foods, such as potato chips or fish bones). When treatment is elected, the lesions may be chiseled off of the cortex or removed via bone bur cutting through the base of the lesion.

Slowly enlarging, recurrent lesions occasionally are seen, but there is no malignant transformation potential. The patient should be evaluated for Gardner syndrome should he or she have multiple bony growths or lesions not in the classic torus or buccal exostosis locations. Intestinal polyposis and cutaneous cysts or fibromas are other common features of this autosomal dominant syndrome.