Odontogenic Tumors of Maxilla
Synonyms: Cysts of maxilla, radicular cysts, dental cysts, dentigerous cysts
Maxillary sinus is closely related to the upper premolar and molar teeth. Any infection / pathology involving the root of these tooth will also have its effect on the maxillay sinus.
Definition: Odontogenic cysts are defined as epithelial cell lined cysts. This lining is derived from the odontogenic epithelium. Most of these odontogenic cysts are defined by their position than by their histology. It is important hence to describe even the site of lesion while sending the surgical specimen to a pathologist.
The following are the cysts of odontogenic origin:
1. Radicular cyst: Synonyms - Peiapical cyst, dental cyst.
This is the commonest of all odontogenic cysts. This is usually caused due to root infection involving the tooth closely related to the maxillary sinus antrum. The resulting pulpal necrosis causes release of toxins at the apex of the tooth leading to periapical inflammation. This inflammation stimulates the Malassez epithelial rests, which are found in the periodontal ligament, resulting in the formation of a periapical granuloma that may be infected or sterile. The epithelium undergoes necrosis and the granuloma becomes a cyst. The cyst could well be sterile if the patient had received antibiotic treatment for dental infection. These lesions when small can easily be missed until and unless a routine radiograph is taken.
Radiographically it is virtually impossible to differentiate granuloma from a cyst. If the lesion is large it is more likely to be a cyst. Radiographically both granuloma and cyst appear to be radiolucent, associated with the apex of non vital tooth.
These lesions can grow into large lesions because they apply pressure over the bone causing erosion. The toxins released by the granulation tissue is one of the common causes of bone erosion. These are non neoplastic lesions. Microscopically, the epithelium is a nondescript stratified squamous epithelium without keratin formation. Evidence of inflammation may be observed in the lining wall.
Clinical features: As the cyst expands it causes erosion of the floor of the maxillary sinus. As soon as it enters the maxillary antrum the expansion starts to occur a little faster because there is space available for expansion. When it reaches a size wherein it fills up the whole antrum, it can erode the anterior wall of the maxilla (in the canine fossa area). This is the weakest portion of the maxillay bone. When it erodes the anterior wall of the maxilla it could cause expansion of the maxilla which could be seen as a swelling in the cheek area. On palpation egg shell crackling may be felt in the anterior wall of the maxilla over the canine fossa. There will be associated tenderness.
Tapping the teeth with a tongue depressor will cause tingling sensation because of involvement of the root of the teeth.
Coronal CT scan showing Dental cyst of right maxilla
Clinical photograph of a patient with dental cyst
Management: If the cyst is small, then it may resolve with endodontic therapy of the involved tooth. If the cyst is large then it will have to excised / marsupialised through Caldwell Luc approach. With the advent of nasal ensoscopy, the lesion could be accessed using a nasal endscope. The excised specimen should be sent for histopathological examination because squamous cell carcinoma could be lurking within the cystic lesion.
2. Dentigerous cyst: This is the second commonest of odontogenic cysts. It is always associated with unerupted tooth. Infact it develops within the normal dental follicle. It is more common over maxillary third molars and maxillary canine tooth areas. This is not considered to be a true neoplasm. Most of these dentigerous cysts are asymptomatic and are incidental discoveries.
The usual radiographic appearance is that of a well-demarcated radiolucent lesion attached at an acute angle to the cervical area of an unerupted tooth. The border of the lesion may be radiopaque. The radiographic differentiation between a dentigerous cyst and a normal dental follicle is based merely on size. While viewing an xray a dentigerous cyst should always be differentiated from a normal dental follicle. In all probability a large sized cyst could only be a dentigerous cyst.
Histologically a normal dental follicle is lined by enamel epithelium, where as dentigerous cyst is lined by non keratinising stratified squamous epithelium. Since the dentigerous cyst develops from follicular epithelium it has more potential for growth, differentiation and degeneration than a radicular cyst. Occasionally the wall of a dentigerous cyst may give rise to a more ominous mucoepidermoid carcinoma. Dentigerous cysts due to its propensity for rapid expansion may cause pathological fractures of jaw bones.
Management: Dentigerous cyst must be excised surgically via a Caldwell Luc approach.
3. Primorial cyst: By definition this cyst develops in place of tooth. This could be due to the fact that formed dental follicle undergoing cystic degeneration instead of odontogenesis. Histologically these lesions are lined by stratified squamous epithelium.
These cysts must be surgically removed.
Gross photograph of primordial cyst
4. Residual cyst: These cysts are caused by retained pericapical cysts after the teeth is removed. The cyst wall is formed by stratified squamous epithelium
5. Lateral periodontal cysts: This is actually a misnomer. These are not inflammatory cysts, and they are not associated with periodontal epithelium. These cysts are associated with lateral canals within the tooth structure. These cysts are always well demarcated, small and radiolucent. The lining epithelium is made of thin cuboidal cells. The cyst wall shows no evidence of inflammation, and is thickened by the presence of fibrous tissue.
These cysts again must be surgically removed.
6. Gingival cysts: are of two types i.e. adult and new born. In newborn these cysts are multiple, but rarely may also be single. They are located in the alveolar ridges. In children these cysts originate from the dental lamina. They are asymptomatic and donot cause any problems. In adults these cysts are commonly found in the lower premolar area. It is usually single.
7. Odontogenic kertocyst: These cysts are very important because of their aggressive behaviour. These cysts are difficult to remove and commonly recur. Histologically these cysts are lined by stratified squamous epithelium which is capable of producing orthokeratin and parakeratin. Commonly both types of keratin are commonly produced. The lumen of these cysts are filled with foul smelling cheesy material. This is nothing but collected degenerated keratin. These cysts commonly give rise to daughter cysts.
These cysts must be completely removed to prevent recurrence. When associated with hypertelorism, midface hypoplasia, relative frontal bossing and prognathism, mental retardation, schizophrenia, multiple basal cell carcinomas, calcification of the falx cerebri, bifid ribs, palmar pitting, it is known as Basal Cell Nevus Syndrome.