A Note on Ameloblastoma: pathogenesis, signs & symptoms, Radiographic features & subtypes...etc

Ameloblastoma

Historically, ameloblastoma has been recognized for over a century and a half. Its frequency, persistent local growth, and ability to produce marked deformity before leading to serious debilitation probably account for its early recognition. Recurrence, especially after conservative treatment, has also contributed to the awareness of this lesion.

Pathogenesis 

This neoplasm originates within the mandible or maxilla from epithelium that is involved in the formation of teeth. Potential epithelial sources include the enamel organ, odontogenic rests (rests of Malassez, rests of Serres), reduced enamel epithelium, and the epithelial lining of odontogenic cysts, especially dentigerous cysts. The trigger or stimulus for neoplastic transformation of these epithelial residues is totally unknown.

Mechanisms by which ameloblastomas gain a growth and invasion advantage include overexpression of anti-apoptotic proteins (Bcl-2, Bcl-xL) and interface proteins (fibroblast growth factor [FGF], matrix  metalloproteinases [MMPs]). Ameloblastomas, however, have a low proliferation rate. Mutations of the p53 gene do not appear to play a role in the development or growth of ameloblastoma.

Signs & symptoms

• Occurs predominantly in the fourth and fifth decades of life
• Appears to be no gender predilection (Slightly more in males)
• Mandibular molar-ramus area is the most favored site
• Slowly growing,
• Painless,
• Hard bony swelling or expansion of jaw,
• Thinning of cortical plates produces “Egg shell crackling”.
• Other symptoms – Tooth mobility, root resorption and paresthesia if inferior alveolar nerve is affected.

RADIOLOGICAL FEATURES

• Typically rounded
• Radiographic margins are usually well defined and sclerotic
• Multilocular radiolucency
• Scalloped margins
• When loculations are large, the appearance is called as “SOAP BUBBLE” appearance

• When loculations are smaller, the appearance is called “HONEY COMBED” appearance.

• Buccal & lingual cortical plates are expanded.
• Roots of adjacent teeth displaced / resorbed.
• As it spreads through medullary spaces, radiographic margins are not accurate indication of bone involvement.
• Desmoplastic ameloblastoma, also has a predilection for the anterior jaws and radiographically resembles a fibroosseous lesion (mixed radiopaque-radiolucent)

DIFFERENTIAL DIAGNOSIS

• ODONTOGENIC KERATOCYST
• FIBROUS DYSPLASIA
• OSSIFYING FIBROMA
• CENTRAL GIANT CELL GRANULOMA

BIOLOGIC SUBTYPES

•         Solid/Multicystic Ameloblastoma
•         Unicystic Ameloblastoma

                        Luminal

Tumor is confined to luminal surface of cyst.

Seen as fibrous cyst wall with lining comprised totally / partially of ameloblastic epithelium, showing a basal layer of columnar / cuboidal reversely polarized cells.

Overlying epithelial cells are loosely adhesive, resembling the stellate reticulum of dental organ.

                        Intraluminal

This variant shows the tumor from cyst lining protruding into the lumen of cyst.

Intraluminal projections resemble plexiform ameloblastoma in most cases, though not always. 

                        Mural

In this type, the fibrous wall of the cyst is infiltrated with typical follicular / plexiform ameloblastoma.

      Believed to be more aggressive than other two variants

•         Desmoplastic Ameloblastoma
•         Peripheral Ameloblastoma

•         Malignant Ameloblastoma
•         Ameloblastic carcinoma   

HISTOPATHOLOGICAL SUBTYPES OF SOLID AMELOBLASTOMA

1. FOLLICULAR

Islands of epithelium resemble dental organ surrounded by mature connective stroma.

Individual follicles show central mass of stellate reticulum like cells surrounded by a single peripheral layer of ameloblast like cells.

Nuclei of peripheral cells are reversely polarized.

       Within the islands, cyst formation is common.

2. PLEXIFORM

Instead of islands, long, anastomosing cords and occasional sheets of epithelial cells bounded by columnar / cuboidal cells.

Cells within cords are more loosely arranged than peripheral cells.

Supporting stroma is loose and vascular.

      Cyst formation occurs, not inside follicles, but in surrounding stroma.

3. ACANTHOMATOUS

Central area of follicles show extensive squamous metaplasia, often associated with keratin formation.

DOEAS NOT INDICATE A MORE AGGRESSIVE COURSE OF TUMOR.

Can be confused with squamous cell carcinoma.

4. GRANULAR CELL

Follicles / sheets of cells show granular cell change.

These cells have abundant cytoplasm filled with eosinophilic granules.

Seen in younger persons and appears to be more aggressive clinically.

5. BASAL CELL TYPE

Least common type

Composed of nests / sheets of hyperchromatic basaloid cells

No stellate reticulum present centrally and peripheral cells tend to be cuboidal rather than tall columnar

TREATMENT

• Can vary from simple enucleation to curettage to en bloc resection.
• As lesion spreads through medullary spaces, simple enucleation can leave islands of tumor within the jaws, leading to recurrence.
• Marginal resection is the optimal method.
• Rarely can undergo malignant transformation.

A Note On Post-Operative Instructions Following Tooth Extraction

Our goal is for your healing process after an extraction to be as comfortable as possible. The removal of teeth is a surgical procedure, and post-operative care is imperative. Please follow all instructions carefully to avoid any unnecessary pain and possible infection. 

 If you have any difficulties or concerns following your surgery, please do not hesitate to call us or return to our office for a follow-up exam. 

Immediately Following Surgery

1. Keep the gauze pad placed over the surgical area with pressure applied by biting down until the bleeding stops. 
2. Take your prescribed pain medication as soon as you begin to feel discomfort. This will usually coincide with the local anesthetic becoming less effective.
3. Do not suck on a straw, spit, or smoke.
4. Restrict your activities the day of surgery, and resume normal activity when you feel comfortable.
5. Place ice packs on the side of your face where surgery was performed. Refer to the section on swelling for an explanation.
6. For mild discomfort, use Ibuprofen (Advil, Motrin). DO NOT take more than 800mg every 4-6 hours.
7. Vigorous mouth rinsing or touching the affected area following surgery should be avoided. This may initiate bleeding caused by dislodging the blood clot that has formed. Do not rinse your mouth for the first post-operative day or while there is bleeding. After the first day, use a warm salt water rinse every 4 hours and after meals to flush out particles of food and debris that may lodge in the area.
8. Restrict your diet to liquids and soft foods which are comfortable for you to eat. 

 Bleeding

A certain amount of bleeding is to be expected following a surgical procedure. Slight bleeding, oozing, or redness in the saliva is not uncommon. Bleeding is best controlled by the use of pressure. Excessive bleeding may be controlled by placing a gauze pad over the area and biting firmly for thirty minutes. Repeat if necessary. If bleeding has not decreased in 3-4 hours, bite on a dampened tea bag placed directly over the surgical site. The tannic acid in the tea helps the blood to clot. 

 Swelling

The amount of swelling that is normally expected after an extraction depends on the type of surgery. Swelling around the mouth, check, eyes, and side of the face is not uncommon.  The swelling sometimes may not appear immediately, and it may occur up to 2-3 days post-surgery. You can help to minimize the swelling by applying ice packs to the affected area.  For the first 3 hours, apply the ice packs directly to the area, alternating on for 20 minutes then off for 20 minutes. Applying ice after 24 hours has no beneficial effect. If swelling or jaw stiffness has persisted for several days, there is no cause for alarm. If the swelling is significant, you may use a moist heat compresses to help suppress it. 

 Pain

Post operative pain will be the most severe the first day after surgery. It is beneficial to take your pain medication before your numbness wears off. For moderate pain, 800mg of Ibuprofen (Motrin or Advil) may be taken every 4-6 hours. For severe pain, take the prescribed medication that was provided. DO NOT take the pain medication on an empty stomach as nausea may result.  The prescribed medicine may make you drowsy. DO NOT drive an automobile or operate machinery, and AVOID alcoholic beverages. Pain or discomfort following surgery should subside more and more each day. If pain persists, it may require attention, and you should contact our office.

 Antibiotics

If you have been placed on antibiotics, take the medicine as directed. Antibiotics may be prescribed to help prevent infection. Discontinue antibiotic use in the event of a rash or other unfavorable reaction. PLEASE NOTE: If you are currently taking birth control pills, they will be inactivated by the antibiotic. 

 Nausea and Vomiting

In the event of nausea and/or vomiting following surgery, DO NOT take anything by mouth for at least an hour, including the prescribed medication. You should then sip on water, tea, or juice. Sip slowly over a fifteen-minute period. When the nausea subsides, you can begin taking solid foods and the prescribed medication. 

Post-Operative Instructions...A Video.