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Diagnosis and Discussion: Ameloblastic Fibroma of the Maxilla
Figure 1. Expansile mass in the left maxilla, loss of the lateral wall of the maxilla, and extension of the mass into the palatine bone. Most of the developing teeth on the left side are not depicted.
Figure 2. Grayish, loose, friable tissue extending from the anterior to the left maxillary tuberosity area.
Figure 3. Islands of odontogenic epithelium in cellular mesenchymal stroma (hematoxylin-eosin, original magnification ×40).
Figure 4. Peripheral columnar cells and central loosely arranged epithelial cells in islands of odontogenic epithelium. Cellular mesenchyme resembles developing dental papilla (hematoxylin-eosin, original magnification ×200).
Histopathologically, the excised neoplasm was composed of islands of odontogenic epithelium, resembling developing enamel organ with peripheral columnar cells and central loosely arranged epithelial cells, and cellular mesenchymal tissue with stellate and spindle-shaped cells resembling developing dental papilla. The mitotic count was low.
Ameloblastic fibroma (AF) is a benign tumor of odontogenic origin. It is composed of proliferative odontogenic epithelium and mesenchymal tissue resembling primitive dental papilla. Comprising approximately 2.5% of odontogenic tumors, AF was first described by Kruse et al1 in 1891. It is more common in children than adults; the average age of onset is 15 years (range, 7 weeks to 42 years).1-3 There is no apparent predilection for race or sex.2,4 The most common clinical presentation is painless facial swelling, although delayed tooth eruption and gingival cysts have been reported as well.4-6 Radiographically, the lesion appears as unilocular or multilocular radiolucencies. Expansion of the cortex is occasionally seen, and involvement with unerupted teeth is common. The lesions are primarily intraosseous ranging in size from 0.5 to 8.5 cm with 80% to 90% of lesions occurring in the mandible.1,4 The clinical differential diagnosis, which requires histopathologic studies, includes neuroectodermal tumor of infancy, ameloblastoma, odontogenic or developmental cyst, ameloblastic fibrosarcoma, and osteogenic sarcoma.
The need for precise histologic diagnosis of AF is uniformly agreed on throughout the literature.6-8 It is histologically similar to 2 other tumors of odontogenic origin: the ameloblastoma and the ameloblastic fibrosarcoma. As of July 1990, Girdler and Edwards2 found only 98 reported cases of AF in the English-language literature. In 1998, Mosby et al1 found only 4 reports of anterior maxillary AF, and they subsequently reported a fifth. Although AF is considered benign, there is still debate over how aggressive one should be in its removal because AF has an 18.3% incidence of recurrence (14 of 82 cases) when treated with simple enucleation and curettage alone.1 Also, it has been found that 44% of the time, ameloblastic fibrosarcoma develops its origins within AF.9 Given the rarity of these tumors, there is limited data regarding the outcome of various surgical approaches. Some have recommended wide local excision as the initial approach,9 while others have concluded that this results in serious disfigurement with unproven long-term benefit.1 In this case, aggressive curettage instead of block resection was performed mainly because of the close proximity of the posterior margin of the tumor to the base of the skull.
Long-term, possibly lifelong, monitoring to detect any recurrence of the tumor will be required for this patient, including clinical and radiographic follow-up every 6 months. Ultimately, bone grafting of the maxillary deformity will be carried out in sequential steps, depending on the growth outcome of the facial bones. The missing teeth will be replaced with implants. Additional surgical intervention in the case of tumor recurrence would include curettage or block resection. Ameloblastic fibroma is not responsive to radiation or chemotherapy. This case constitutes the sixth reported case to our knowledge.
Accepted for publication September 15, 1999.
We thank John R. Kalmar, DMD, PhD, for his assistance in the histopathologic diagnosis.
Reprints: Paul F. Lehoullier, MD, PhD, Rochester General Pediatric Associates, Rochester General Hospital, 1425 Portland Ave, Rochester, NY 14621.
Pathological Case of the Month. Arch Pediatr Adolesc Med. 2001;155(6):736. doi:10.1001/archpedi.155.6.735
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