Ameloblastoma

Four types of ameloblastoma have been described by the WHO 2017 classification: • Conventional (solid/multicystic) type ameloblastoma • Unicystic ameloblastoma • Peripheral/extraosseous ameloblastoma • Metastasizing ameloblastoma Conventional ameloblastoma Previously known as solid/multicystic ameloblastoma. Usually presents with multiple large cystic areas. Unicystic ameloblastoma Ameloblastoma with a single cyst cavity account for around 10% of ameloblastomas. Present in younger patients in their second and third decades of life, often in relation to unerupted third molar. Metastasising ameloblastoma Histologically atypical ameloblastoma can, rarely, lead to metastasis, usually in the lung. 'Metastasis' look histologically identical to the primary tumour and are benign in nature. Peripheral ameloblastoma The peripheral subtype composes 2% of all ameloblastomas. ==Presentation==

Ameloblastomas can be found both in the maxilla and mandible. Although, 80% are situated in the mandible with the posterior ramus area being the most frequent site. The neoplasms are often associated with the presence of unerupted teeth, displacement of adjacent teeth and resorption of roots. Symptoms include a slow-growing, painless swelling leading to facial deformity. As the swelling gets progressively larger it can impinge on other structures resulting in loose teeth and malocclusion. Bone can also be perforated leading to soft tissue involvement. ==Histopathology==

Conventional ameloblastomas have both cystic and solid neoplastic structures. Solid structure Solid areas contain fibrous tissue islands or epithelium that interconnect through strands and sheets. The epithelial cells tend to move the nucleus away from the basement membrane to the opposite pole of the cell. This process is called reverse polarization. Two main histological patterns most often occur: follicular and plexiform. Other less common histological variants include acanthomatous, basal cell, and granular cell patterns. A systematic review showed a predilection for males and predominance in fourth and fifth decades in life. 52% of the cases of desmoplastic ameloblastomas showed mandibular involvement, with a tendency to anterior region. The majority of the tumors were found to have ill-defined margins radiographically. ==Diagnosis==

Ameloblastoma is tentatively diagnosed through radiographic examination and must be confirmed by histological examination through biopsy. Radiographically, the tumour area appears as a rounded and well-defined lucency in the bone with varying size and features. Numerous cyst-like radiolucent areas can be seen in larger tumours (multi-locular) giving a characteristic "soap bubble" appearance. A single radiolucent area can be seen in smaller tumours (unilocular). Lingual plate expansion is helpful in diagnosing ameloblastoma as cysts rarely do this. Resorption of roots of involved teeth can be seen in some cases, but is not unique to ameloblastoma. Differential diagnosis • Keratocystic odontogenic tumour • Central giant-cell granuloma • Odontogenic myxoma ==Treatment==

is difficult in this child with a large ameloblastoma.|alt= Chemotherapy, radiation therapy, curettage, and liquid nitrogen have been effective in only very rare cases of ameloblastoma, so surgical resection or enucleation are the recommended treatment options. In a detailed study of 345 patients, chemotherapy and radiation therapy were contraindicated for the treatment of ameloblastomas. A systematic review found that 79% of desmoplastic ameloblastoma cases were treated by resection. Conservative treatment requires very careful case selection. A systematic review found that 79% of desmoplastic ameloblastoma cases were treated by resection. Chemotherapy is also often ineffective. and some indication that some ameloblastomas might be more responsive to radiation than previously thought. Follow up is important, because 50% of all recurrences occur within 5 years postoperatively. Follicular variants appear to recur more than plexiform variants. Seeding to the bone graft is suspected as a cause of recurrence. Recurrence has been reported to occur as many as 36 years after treatment. To reduce the likelihood of recurrence within grafted bone, meticulous surgery SMO mutations activate the hedgehog signaling pathway, yielding results similar to V600E, but are less frequently seen. There is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas. ==Epidemiology==

People with African heritage have been shown to have a higher incidence compared to Caucasians, with the site often being in the midline of the mandible. Ameloblastomas account for about one percent of all oral tumors Men and women are equally affected, though women average four years younger than men when tumors first occur, and tumors run larger in females. == See also ==