Ameloblastic fibroma is a tumor of mixed connective and odontogenic tissue origin, most commonly found in the young age groups of 15–25 years; the male population is affected more than the female population. It presents frequently in the mandible than in the maxilla, usually in the canine to molar region. Clinically, the tumor grows slowly and painlessly, expanding the jaw.
Radiographic appearance is identical to that of unicystic ameloblastoma with area of radiolucency and smooth outline especially if unerupted teeth are involved. Both lesions affect similar age groups and have similar clinical appearances. Histologic examination differentiates the two 1–3.
Histologically, the tumor consists of strands of epithelial cells in a connective tissue background and does not invade the bone. These cells are arranged irregularly with branching strands that have some resemblance to the dental lamina.
The connective tissue resembles cellular fibroblastic tissue similar to dental pulp in the developing tooth, with occasional collagen bands and sometimes hyaline-like tissue seen adjacent to the epithelial strands. The epithelial and connective tissue components grow together inside a capsule.
The tumor is distinguished from ameloblastomas by the fact that both the epithelial and mesenchymal components are neoplastic, whereas in ameloblastomas only the epithelium is neoplastic 4.
Ameloblastic fibroma is a benign lesion and treatment is by block excision with a border of normal bone. With simple excision or enucleation, recurrence rates of 20–40% have been reported. Sarcomatous change (ameloblastic fibroma) has been reported with recurrence or inadequate excision 5. From 23 cases reported only two recurrences have been found 6.
A follow-up over a longer period found a recurrence rate of 43.5%, which suggested the tumor might be more difficult to excise than originally thought and wide resection is not usually required 7,8.
Other forms include the ameloblastic fibro-odontoma, which occurs more often in the upper jaw. Malignant variations are rare, and include ameloblastic fibrosarcoma and ameloblastic odontofibrosarcoma.
A 17-year-old girl was referred by the community dental service. The presenting problem was swelling and excruciating pain in the buccal space distal to the maxillary-impacted third molars on both sides. The pain had started about 5 months earlier, increasing gradually, and disturbed eating and sleeping functions.
Oral examination revealed limitation in mouth opening. All teeth were fully erupted, except the maxillary and mandibular third molars.
Panoramic radiograph of the patient confirmed bilateral maxillary-impacted third molars, showing diffuse areas of radiolucency, and the lesion appeared with fairly well-circumscribed borders (Fig. 1).
The differential diagnosis was dentigerous cyst.
The buccal space distal to the maxillary third molars on both sides was investigated carefully under general anesthetic and found to consist of firm, grayish-white tissue.
Surgical extraction of the bilateral maxillary-impacted third molars together with excision of the tumor was performed. Panoramic radiograph of the patient was taken subsequent to this (Fig. 2).
Samples sent for histopathologic examinations were reported as follows: sections revealed fibrous stromal tissue that showed areas of enclosed strips of epithelial cells. These strips were formed of two layers of small cells. Focal area showed calcification with more hypercellularity (Figs 3 and 4).
These findings were consistent with ameloblastic fibroma.
Three years after the initial surgery, the patient complained of mild pain on the right side of the posterior maxilla. The patient underwent further surgery, and block excision of the remaining tumor tissue was performed. Follow-up examination 12 months later revealed the patient to be free of symptoms.
The majority of ameloblastic fibromas have been reported in the mandible 9–12.
Unusual presentations include an ameloblastoma in association with ameloblastic fibroma in a 5-year-old boy 13, a cystic ameloblastic fibroma in a 7-year-old boy 14, and ameloblastic fibroma in a 1-year-old girl 15.
The distinction must be made between ameloblastic fibroma and peripheral ameloblastic fibroma; the latter is a true mixed tumor, and in that case report it was found that the lesion had occurred within the gingival rather than bony tissue 16.
In the case reported here, the main presenting feature was persistent excruciating pain with enlargement of the buccal gingiva right and left posterior maxilla distal to the third molars.
Radiographic investigation showed radiolucency associated with crowns of unerupted third molars. Differential diagnosis was a dentigerous cyst.
Surgical investigation and histopathological examinations revealed the lesion to be benign tumor of odontogenic origin.
What is unique is that the lesion was symptomatic and occurred bilaterally in this patient. Recurrence might be due to incomplete removal and presence of satellite tumors at the edge of the lesion, which occurred on one side but not both sides. This type of episode has never been reported in any journal.
Ameloblastic fibroma is an uncommon tumor that must be carefully and correctly diagnosed and treated. Follow-up should be for a long period of at least 3–5 years to enable detection of possible recurrence or development of ameloblastic fibrosarcoma, which is the malignant counterpart.
Dr Ahmad Hany El-Barkouky, MD performed the histopathology examination of the lesion.
Conflicts of interest
There are no conflicts of interest.
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