Non-Neoplastic Lesions of the Gnathic Bones

Clinical Features

Osteomyelitis is uncommon in the head and neck, but poor oral hygiene, tobacco use, alcoholism, malnutrition, and immunosuppression are associated findings. Patients with acute osteomyelitis show all signs and symptoms of an acute inflammatory disease, such as fever, malaise, and regional lymphadenopathy. Often a dental infection, extraction, or surgery may incite the initial infection, whereas fractures may introduce oral flora into the bony interstices. In chronic osteomyelitis, signs and symptoms usually are less prominent and may fluctuate in severity; they include swelling, pain, sinus formation, sequestration, and, in case of bone loss, pathologic fractures. The disease may occur at any age, but jaw disease seems to be more common in the sixth to seventh decades, with males affected more often than females. The mandible is more commonly involved (usually posterior body), but the maxilla is more often affected in children and infants due to a greater surface area and more rich blood supply. Many different organisms are etiologically related, but pneumococcus and Haemophilus influenzae are most common.

Sclerosing osteomyelitis and proliferative periostitis are specific subtypes. Sclerosing osteomyelitis causes recurrent pain, swelling of the cheek, and restricted jaw movement and may be either diffuse or focal. Proliferative periostitis is a periosteal reaction to inflammatory changes in the underlying jaw bone causing facial swelling and bony enlargement.

Radiographic Features

Radiographs show an irregular pattern of bone loss and increased density of bone, but generally only after 3 weeks of disease. Plain films are difficult to interpret, whereas MRI is much better at identifying extent of disease and showing bone marrow and soft tissue involvement, highlighting sequestration. Bone scan, considered to be the most sensitive study, is able to see hyperperfused tissues 2 to 3 days after an infection. However, there is a low specificity. Cortical duplicating or “onion-skinning” is the radiographic hallmark of proliferative periostitis.

Pathologic Features

Microscopic Findings

Marrow fibrosis or edema is the hallmark of osteomyelitis, with bone necrosis identified by marrow fibrosis and inflammation. It is important not to overinterpret lack of osteocytes as necrosis, especially if there is over-decalcification. Acute osteomyelitis shows necrotic bone fragments with neutrophilic granulocytes and thick layers of microorganisms ( Fig. 14.1 ). Bone death is present, with bone resorption identified by osteoclastic activity and release of neutrophil neutral proteases. Subacute disease shows both neutrophils and chronic inflammatory cells, coupled with marrow fibrosis, bone death, and resorption. In chronic osteomyelitis, sclerotic bone masses combine with chronic inflammation and dense fibrosis ( Fig. 14.2 ). New bone formation is often seen. Squamous lined fistulae/sinuses may extend from the oral mucosa.

In case of proliferative periostitis, one sees bony trabeculae that lie in a linear parallel pattern ( Fig. 14.3 ).

Differential Diagnosis

Acute osteomyelitis generally does not pose any differential diagnostic problems, although fracture repair is sometimes considered. There is generally a lack of acute inflammation and dead bone. Chronic osteomyelitis may be confused with fibrous dysplasia, osseous dysplasia, Paget disease, or osteonecrosis. Paget disease shows highly vascular bone marrow with abundant osteoclasts. A mosaic pattern of reversal lines in the bone is not a reliable diagnostic tool as this can occur in osteomyelitis as well. Fibrous dysplasia is distinguished from chronic osteomyelitis by its slender trabeculae of woven bone that differ from the sclerotic lamellar bone masses in osteomyelitis. Osteonecrosis usually shows bone death and necrosis with very active remodeling and chronic inflammation. A radiation or drug therapy (such as bisphosphonates) history can generally be elicited. The main differential diagnostic problem occurs with osseous dysplasia, which sometimes also consists of large masses of sclerotic lamellar bone. Criteria that may be useful in this context are discussed under that specific heading. Sinuses or fistulae lined by squamous epithelium should not be confused with squamous cell carcinoma infiltrating the bone. Absence of cellular atypia rules out this possibility. Rarely, lymphoma may be seen within a setting that can mimic osteomyelitis.

Prognosis and Therapy

Treatment of acute osteomyelitis consists of antibiotics and removal of dead bone. It is imperative to obtain cultures and use appropriate drug therapy, often for a prolonged period and sometimes as intravenous therapy (for base of skull disease). Chronic osteomyelitis is more difficult to manage, unless all necrotic bone and organisms are removed. Foreign objects should be removed to prevent a nidus of recurrent infection. In some cases, bone grafts are used for bone stability and reconstruction.

Clinical Features

The most common developmental cyst, dentigerous cysts account for approximately 25% of all jaw cysts. They occur twice as often in males as in females and have the highest incidence between 10 and 40 years of age (mean, 33 years), although seen over a wide age range. The mandible is affected twice as often as the maxilla, where the mandibular third molars are most commonly affected, followed by maxillary canines, maxillary third molars, and then mandibular second premolars. Usually identified in asymptomatic patients during routine radiographs, it is only when they are large that they result in pain, resorption of adjacent teeth, and possible infections.

Radiographic Features

Dentigerous cysts present as unilocular radiolucent lesions with a well-defined sclerotic border, into which the crown of an unerupted tooth protrudes ( Fig. 14.4 ). However, there may be a central, lateral, or circumferential relationship to the crown of the tooth. The cyst may be multilocular when large, associated with tooth displacement.

Pathologic Features

Microscopic Findings

The cyst wall is lined by a thin layer (usually 2-3 cells thick) of cuboidal to squamoid epithelium ( Fig. 14.5 ). The epithelium may be significantly thickened if associated with inflammation, resulting in hyperplastic rete ridges. Cholesterol clefts and Rushton bodies (degenerated, hypereosinophilic keratin flakes) may be seen. Mucous cells, sebocytes, and ciliated cells may be observed ( Fig. 14.5 ). The cyst wall, composed of fibrous or fibromyxoid connective tissue, may contain varying amounts of odontogenic epithelial nests (up to 20% of cases) and occasional dystrophic calcifications.

Differential Diagnosis

An eruption cyst (dental follicle) is a specific type of dentigerous cyst located in the gingival soft tissues overlying the crown of an erupting tooth. It generally lacks a cystic epithelium and is usually less than 3 to 4 mm in size. Although there is radiographic overlap, histologic examination will separate odontogenic keratocyst and unicystic ameloblastoma from dentigerous cyst. Odontogenic keratocysts are lined by a basal palisade of epithelial cells with a characteristic superficial corrugated parakeratosis. Unicystic ameloblastoma shows a basal layer of cylindrical cells with hyperchromatic nuclei, occasional reverse polarity, and an overlying layer of spindle-shaped cells with intervening edema resembling stellate reticulum. Fibromyxomatous areas in the connective tissue wall of the dentigerous cyst may be confused with an odontogenic myxoma. However, myxomas are not cystic and lack an epithelial lining. Glandular odontogenic cyst develops in the fifth decade, usually associated with cortical perforation of the anterior mandible. There is a squamous epithelium that shows plaque-like thickenings or whorls; hobnail cells and duct-like structures may be seen.

Prognosis and Therapy

Removal of the cyst wall and extraction of the involved tooth will yield a permanent cure, although sometimes marsupialization is used for large cysts. There is a very low rate of recurrence.

Clinical Features

Periapical cyst is the most common jaw cyst and accounts for approximately 75% of periapical lesions. There is a wide age range and equal sex distribution. Most patients are asymptomatic, with lesions identified by routine dental imaging. When there is inflammation, then pain, sensitivity to temperature changes, and swelling may be seen. In general, caries result in tooth cavitation, resulting in bacterial invasion of the tooth pulp, which results in tooth devitalization.

Radiographic Features

In general, there is a radiolucent lesion located at the root tip of a nonvital tooth, often associated with root resorption ( Fig. 14.6 ). The radiolucency must be associated with the tooth root or lateral root surface. There may be caries, fracture, restoration, or other endodontic apparatus in place.

Pathologic Features

Microscopic Findings

The cysts are lined by nonkeratinizing squamous epithelium that may show elongated rete processes ( Fig. 14.6 ). Cholesterol clefts with foreign body giant cells are frequently present ( Fig. 14.7 ). Chronic inflammation is prominent and stromal calcifications may be seen. Intraepithelial hyaline bodies, so-called Rushton bodies, may be present, but these are not a specific finding ( Fig. 14.7 ).

Differential Diagnosis

Given the fact that the histology is nonspecific, other jaw cysts, both odontogenic and nonodontogenic, can give an identical appearance, especially in cases with extensive inflammation. Therefore, it should be noted that a periapical cyst is strongly associated with the root of a decayed and nonvital tooth. A nasopalatine duct cyst may be confused with central maxilla lesions, but the histologic features are characteristic.

Prognosis and Therapy

Tooth extraction or apical resection with curettage of the periapex usually is an adequate treatment. Endodontic treatment with a root canal may be used with tooth restoration. Antibiotic therapy is often used for infections. When a cyst is left behind after extraction of the corresponding tooth, it is called a residual cyst.

Clinical Features

Fibrous dysplasia occurs predominantly in children and adolescents. The maxilla is more often involved than the mandible. Polyostotic disease is more common in females and shows craniofacial involvement in virtually all cases. Bone pain, fractures, and deformity are the most common presenting features. Skull base involvement may lead to cranial nerve compression with corresponding neurologic symptoms. When part of McCune-Albright, nearly all cases are diagnosed before 15 years of age.