J Oral Maxillofac Surg60:216-218, 2002

Ameloblastic Fibroma: Report of a CaseSu-Gwan Kim, DDS, PhD,* and Hyun-Seon Jang, DDS, PhD

Ameloblastic broma (AF) is a relatively rare, slow-growing, benign odontogenic tumor. It is usuallyasymptomatic except for the eventual expansion ofthe jaw.1-3 AF is most common in adolescents andyoung adults, and is generally found in the mandible.This report describes a 3-year-old girl with AF in themandible. The differential diagnosis, histology, andtreatment are discussed.

Report of a Case

A 3-year-old girl was referred to our hospital on January22, 1999 after a swelling developed in the right cheek a fewdays after trauma to that area. Her medical, surgical, family,and social histories were unremarkable. A systemic reviewwas within normal limits, and no medication had beenadministered.Intraoral examination showed a hard swelling in the right

mandibular body. A panoramic radiograph showed a large,multilocular, radiolucent lesion with scalloped margins. Itextended from the right rst deciduous molar area to theascending ramus and coronoid process (Fig 1). The radio-graph also revealed expansion of the cortex and resorptionof the roots of the lower right second deciduous molar. Adisplaced, developing permanent rst molar was associatedwith the lesion. The clinical diagnosis was dentigerous cyst.Enucleation of the lesion, extraction of the lower rightpermanent rst molar crown, and open packing were per-formed under general anesthesia. During the surgery, thelesion was found to be encased in bone. It measured 4 3 16 cm, was dark brown, and was soft in consistency. Itwas removed in pieces and the surrounding bone wascuretted. The inferior alveolar nerve was preserved duringthe procedure and the patient retained normal sensation.Furacin gauze was used as the packing material. Packingwas continued for 30 days and the gauze was changed daily.Microscopic examination of the tissue showed the pres-

ence of dental lamina-like strands, cords, and nests of odon-togenic epithelium within a dental papilla-like myxomatousmesenchymal matrix (Fig 2). Positive cytokeratin stainingwas seen in the odontogenic epithelium, while positive

vimentin staining was observed in some areas of the imma-ture, dental papilla-like cells and in the basement membraneof the odontogenic epithelium (Figs 3, 4). No tumor wasfound in the tissue curetted from the surrounding bone.The nal diagnosis was ameloblastic broma.Different areas of the specimen showed different histo-

logic ndings (Figs 5, 6). No calcied dental structures wereapparent in the specimen. Areas of mesenchymal tissuewithout epithelial strands were present, and large areasdevoid of ameloblastic strands and dental papilla were alsoseen (Fig 5). Mesenchymal growth appeared to be moreactive in areas devoid of epithelium (Fig 6).The postoperative course was uneventful and the patient

was discharged for further follow-up. Healing was unevent-ful and there were no signs of recurrence 22 months aftersurgery (Fig 7).

Discussion

AF is a relatively rare, benign neoplasm of thegroup of mixed odontogenic tumors. It representsonly 2% of odontogenic tumors.4 It is characterized bythe simultaneous proliferation of epithelial and mes-enchymal tissue, without the formation of dentin orenamel.5 AF is a true mixed tumor in which both theepithelial and ectomesenchymal elements are neo-plastic. There are 2 rare variants: granular cell AF andperipheral AF.6

The precise etiology of AF is not known. However,it is believed to arise de novo during a particular stageof odontogenesis, possibly as a result of overzealouselaboration of the basal lamina without further odon-togenic differentiation.7

Trodahl8 reported that in 58% of cases the present-ing symptom is swelling. Moreover, there is no signif-icant gender difference in the frequency of AF or racepredilection.8 It has been reported as occurring atages ranging from 6 months to 42 years, with anaverage from 14.6 to 15.5 years. The youngest patientwas a 7-week-old infant reported recently.9,10 Over80% of these tumors occur in the mandible, usually inthe canine-molar region.11,12 Only 4 tumors have beenreported in the anterior maxillary region.13

AF exhibits somewhat slower growth than amelo-blastoma, and does not tend to inltrate. Instead, itenlarges by gradual expansion so that the peripheryof the lesion often remains smooth. The tumors fre-quently go unnoticed by patients, and are discoveredaccidentally during radiographic examination. Pain,tenderness, or mild swelling of the jaw may promptthe patient to seek relief from a dentist. In the casepresented, the chief complaint was swelling of thecheek.

Received from the College of Dentistry, Chosun University, Kwang-

Ju, Korea.

*Assistant Professor, Department of Oral and Maxillofacial Sur-

gery, Oral Biology Research Institute.

Lecturer, Department of Oral Pathology.

Address correspondence and reprint requests to Dr Kim: De-

partment of Oral and Maxillofacial Surgery, College of Dentistry,

Chosun University, 421, SeoSeogDong, DongKu, KwangJu City,

Korea; e-mail: SGCKIM@mail.chosun.ac.kr

2002 American Association of Oral and Maxillofacial Surgeons

0278-2391/02/6002-0017$35.00/0

doi:10.1053/joms.2002.29829

216

FIGURE 1. A panoramic radio-graph showing a multilocular os-teolytic lesion in the mandibularbody and ramus.

FIGURE 2. Dental lamina-like strands, cords, and nests of odonto-genic epithelium are seen within a dental papilla-like myxomatousmesenchymal matrix (hematoxylin-eosin stain, original magnication200).

FIGURE 3. Positive cytokeratin staining is observed in the odonto-genic epithelium (original magnication 200).

FIGURE 4. Positive vimentin staining is observed in some immaturedental papilla-like cells as well as in the basement membrane of theodontogenic epithelium (original magnication 200).

FIGURE 5. Large areas devoid of ameloblastic strands and dentalpapilla are seen (hematoxylin-eosin stain, original magnication40).

KIM AND JANG 217

Radiographically, AF usually appears as a multilocularradiolucency with sclerotic margins. It typically rangesfrom 1 to 8 cm in diameter.1 Smaller tumors may appearunilocular, whereas larger ones may extend through thecortices of the bone.1 In the case presented, a multiloc-ular osteolytic image was observed.Histologically, both the epithelial and connective

tissue components of AF are neoplastic. The epithelialcomponent is usually in the form of strands and is-lands, and often has a peripheral layer of cuboidal orcolumnar cells. The central area resembles the stellatereticulum of the embryonic enamel organ. Mitoticactivity is uncommon. In fact, if mitotic activity isreadily apparent, particularly in the mesenchymal el-ement, the pathologist should consider the possibilityof malignant transformation. The connective tissuecomponent is much more cellular than in ameloblas-toma. The cells mimicking the dental papilla or prim-itive pulp tissue are round or angular, and there islittle surrounding collagen. The degree of cellularity

varies within the same tumor and between tumors.A denite capsule is considered an unusual featureof AF.Various immunohistochemical markers of intra

and extracellular proteins have been studied in AFand other benign odontogenic mixed tumors. Pro-liferating cell nuclear antigen and MIB-1 are pro-teins recently well-recognized in relation to cellularproliferating activity.14 Evaluation of the growthpotential in AF and related lesions could be of helpin understanding tumor aggressiveness and in se-lecting appropriate surgical procedures. In thepresent case, immunohistochemical staining for cy-tokeratin and vimentin was performed and the tu-mor cells stained positively.The differential diagnosis includes ameloblastic -

brosarcoma.15 AF is treated by enucleation and curet-tage of the surrounding bone and removal of theaffected teeth.16 Although recurrence of AF is rare,long-term follow-up is recommended.4 Recurrence isa result of conservative treatment with regrowth ofresidual tumor, often aided by an attempt to retaininvolved teeth.

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Tumors of the Oral Tissues (ed 5). Hong Kong, ChurchillLivingstone, 1998, pp 65-69

2. Shafer WG, Hine MK, Levy BM: A Textbook of Oral Pathology(ed 4). Philadelphia, PA, Saunders, 1983, pp 304-306

3. Regezi JA, Sciubba JJ: Oral Pathology: Clinical-Pathologic Cor-relations. Philadelphia, PA, Saunders, 1989, pp 393-394

4. Blankestijn J, Panders AK, Wymenga JP: Ameloblastic bromaof the mandible. Br J Oral Maxillofac Surg 24:417, 1986

5. Regezi JA, Kerr DA, Courtney RM: Odontogenic tumours:Analy-sis of 706 cases. J Oral Surg 36:771, 1978

6. Takeda Y: Ameloblastic broma and related lesions: Currentpathologic concept. Oral Oncol 35:535, 1999

7. Eversole LE, Tomich CE, Cherrick HM: Histogenesis of odon-togenic tumors. Oral Surg 32:569, 1971

8. Trodahl JN: Ameloblastic broma: A survey of cases from theArmed Forces Institute of Pathology. Oral Surg 33:547, 1972

9. Slootweg PJ: An analysis of the interrelationships of the mixedodontogenic tumors: Ameloblastic broma, ameloblastic bro-odontoma and the odontomas. Oral Surg 51:266, 1981

10. Mosby EL, Russel D, Noren S, et al: Ameloblastic broma in a7-week-old infant: A case report and review of the literature.J Oral Maxillofac Surg 56:368, 1998

11. Zallen RD, Preskar MH, McClary SA: Ameloblastic broma.J Oral Maxillofac Surg 40:513, 1982

12. Young AH: Ameloblastic broma in an infant. J Oral MaxillofacSurg 43:289, 1985

13. Heringer WW: Ameloblastic broma in an anterior maxilla:Report of a case. J Dent Child 45:408, 1978

14. Yamamoto K, Yoneda K, Yamamoto T, et al: An immunohisto-chemical study of odontogenic mixed tumors. Oral Oncol31:122, 1995

15. Leider AS, Nelson JF, Trodahl JN: Ameloblastic brosarcoma ofthe jaws. Oral Surg Oral Med Oral Pathol 33:559, 1972

16. Dallera P, Bertoni F, Marchetti C, et al: Ameloblastic broma: Afollow-up of six cases. Int J Oral Maxillofac Surg 25:199, 1996

FIGURE 6. Active mesenchymal growth is present (hematoxylin-eosinstain, original magnication 100).

FIGURE 7. A postoperative panoramic radiograph showing no evi-dence of recurrence 22 months after surgery.

218 AMELOBLASTIC FIBROMA: REPORT OF A CASE