Ameloblastoma natural history, complications and prognosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]

Overview

If left untreated, [#]% of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3]. Common complications of [disease name] include [complication 1], [complication 2], and [complication 3]. Prognosis is generally excellent/good/poor, and the 1/5/10-year mortality/survival rate of patients with [disease name] is approximately [#]%.

Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as poor/good/excellent.

Natural History

• The majority of ameloblastomas expand slowly, they do so by infiltrating into the adjacent bone marrow and, if allowed to grow until there is extensive jaw expansion, they may penetrate the cortex and extend into muscle and other local soft tissues. The resulting tumors or cysts are usually benign but the tissue growth may be aggressive in the involved area. On rare occasions, tissue near the jaws, such as around the sinuses and eye sockets, may become involved as well. The tissues involved are most often those that give rise to the teeth so that ameloblastoma may cause facial distortion. Malignancy is uncommon as are metastases, but they do occur. Ameloblastoma is characterized by an abnormal growth in the jaw or sinus area, often at the site of the third molar. The tumors or cysts may be aggressive and may spread to the eye socket, nose, and skull.
• Although ameloblastoma is considered a benign odontogenic tumor, it is locally aggressive, slow growing, and has a high propensity for local recurrence if not removed completely.
• It is important for ameloblastoma to be diagnosed and treated early in order to stop growth of the tumors and possible progression to cancer. Although it is uncommon, ameloblastomas have been known to become malignant and spread to other parts of the body, especially to the lungs.
• Ameloblastomas have a significant recurrence rate traditionally ranging between 5% and 30% over periods ranging from 5 to 15 years, thus necessitating resection. The initial surgical treatment must be carefully and scrupulously done to avoid recurrence. Ameloblastomas do not usually become malignant. Evidence suggests that ameloblastoma is more likely to become malignant if the condition reoccurs after surgery.The initial surgical treatment must be carefully and scrupulously done to avoid recurrence.

Complications

According to World Health Organization (WHO) ameloblastoma is a benign tumor. Metastases to the lungs or central nervous system (CNS) have rarely been reported. Complications of ameloblastoma include the following:

• Breathing difficulty
• Pain and facial deformity
• Secondary infection of the tumor
• The recurrence rate of these tumors is 25-30%. The tumor can recur after treatment and hence, a close follow-up is needed.

Prognosis

• The prognosis of ameloblastoma was associated mainly with the method of surgical treatment, which means that patients receiving a radical treatment had a better prognosis than those who received a radical one. It seemed that the best way for treating the ameloblastoma was extensive resection of the tumor with a wide region in the normal bone.

In majority of patients the radical surgery is a best choice, but not for all. In more than 50% patients receiving the conservative treatment had good prognosis without any recurrence. In other words, more than 50% patients could be treated by a conservative method, and maintain the continuity of their jaws to have a better quality of life.

• Many factors were related with the prognosis of ameloblastoma.
• It is valid to use radiographs to estimate the growth rate of focal osseous lesions in clinical practice. The biological behavior of the ameloblastoma was related to the radiographic appearance, and the multilocular type of ameloblastoma had a poor prognosis. The radiographic boundary of ameloblastoma is a useful parameter in evaluating the growth rate of the tumor. Scientists have also stated that, while ameloblastomas invaded the intertrabecular spaces of cancellous bone, they do not invade compact bone, although they may erode it. Ameloblastoma which has a well-defined edge with sclerosis is thought to grow slowly, and the normal bone has a strong reaction to form the sclerosis edge, which acts like compact bone to resist the invasion of the tumor, even if the size of the lesion is comparably large. So the tumor is confined and the prognosis is good. On the contrary, if the tumor's radiographic boundary is not sclerotized, the tumor was thought to be a little more aggressive and the prognosis is not so good. Ameloblastomas with ill-defined boundary are thought to have the most aggressive behavior than others, which should be treated by the radical surgery because of the higher recurrent probability. With the ill-defined radiographic boundary, the tumor has the highest proliferative ability and poorest prognosis.
• Scholars believe that a radical surgery should be used for the multicystic ameloblastoma to prevent the recurrence. The follicular ameloblastomas were thought to have a higher recurrence rate than unicystic or plexiform. Scientists have found that ameloblastoma in children was mainly the plexiform type, and conservative treatment could be accepted as the initial treatment. Due to lack of the cortical plates, ameloblastoma in maxilla was thought to spread readily into the adjacent vital regions and suggested to be treated by extensive resection.