Ossifying Fibroma Misdiagnosed as Chronic Apical Periodontitis Fla ´via Maria de Moraes Ramos-Perez, DDS, PhD,* Ulysses Nicida Soares, DDS, † Yara Teresinha Correˆa Silva-Sousa, DDS, PhD,* and Danyel Elias da Cruz Perez, DDS, PhD* Abstract Introduction: Ossifying fibroma mimicking chronic apical periodontitis is extremely rare. This report describes a case of ossifying fibroma located in the peri- apical region of the mandibular right canine that was misdiagnosed as chronic apical periodontitis. Methods: A 40-year-old woman complained of slight pain in the right anterior mandibular region without mucosal abnor- malities or swelling. Radiographically, a well-circum- scribed, unilocular, radiolucent lesion was observed that was located in the periapical region of the mandib- ular right canine, which presented an endodontically treated root canal. Under local anesthesia, the lesion was fully excised. Results: Microscopically, there was fibrocellular connective tissue associated with a mineral- ized component, which consisted of lamellar or trabec- ular and woven bone, compatible with the diagnosis of ossifying fibroma. Conclusions: Although it is very rare, ossifying fibroma should be considered in the differential diagnosis of unusual or persistent apical radiolucencies. (J Endod 2010;36:546–548) Key Words Misdiagnosis, ossifying fibroma, periapical lesions, persistent apical periodontitis M ost periapical lesions are of endodontic origin as consequence of root canal infec- tion and necrosis. However, some nonendodontic pathoses might present as peri- apical radiolucencies and eventually lead to misdiagnosis, particularly if the lesion involves an endodontically treated tooth or one with pulp necrosis (1–3). Ossifying fibroma (OF) is a relatively rare benign neoplasm of the jaws, composed of connective tissue of mixed and variable cellularity, with a mineralized component that consists of trabecular or woven bone (4). It occurs most commonly in patients between the second and fourth decades of life, with a female predilection. The posterior region of the mandible is the most common site. Radiographically, the OF usually presents as a well-delimited, mixed radiopaque and radiolucent lesion (5, 6). Depending on the quantity of mineralized tissue, the lesion can present predominantly as a radiolucent or radiopaque image (5). Although a number of periapical reactive and neoplastic lesions have been described, OF mimicking chronic apical periodontitis is extremely rare (7, 8). The aim of this report is to describe a case of OF that was apparently misdiagnosed as chronic apical periodontitis. Case Report The patient, a 40-year-old woman, presented to a private dental clinic complaining of slight pain in the right anterior mandibular region of 5-month duration. On intraoral examination, the gingival and alveolar mucosa of the mandibular right canine region showed normal features without swelling. However, during palpation buccal bone cortical fragility was noted, and the patient reported exacerbation of the symptoms. Radiographically, a well-circumscribed, unilocular, radiolucent lesion was observed, located in the periapical region of the mandibular right canine and measuring about 1.0 cm in diameter. Moreover, there was disruption of the lamina dura, the root canal of the abovementioned tooth had been endodontically treated, and the lesion extended into the apical region of the adjacent lateral incisor (Fig. 1). In view of the radiographic findings, the patient was asked about the endodontic treatment, but she did not know the reasons why or the time when it was performed. The mandibular right first premolar, lateral and central incisors responded positively to a cold pulp test. Accord- ing to the clinical and radiographic features, persistent apical periodontitis and an odontogenic cyst or tumor were the main diagnostic hypotheses. Thus, under local anesthesia, the lesion was fully excised, without complications. During surgical exci- sion, a thin buccal bone cortical plate was observed, and the lesion, composed of friable tissue, was well-demarcated, without merging with the cortical bone. Microscopically, there was fibrocellular connective tissue associated with a miner- alized component, which consisted of lamellar or trabecular and woven bone (Fig. 2). No necrosis, mitosis, and nuclear pleomorphism were observed. Therefore, the diag- nosis of OF was established. Eight months after excision there was complete bone formation. The patient was under clinical and radiographic follow-up for 3 years, and no signs or symptoms of recurrence were observed. Discussion Although most periapical lesions are a consequence of dental pulp necrosis, about 0.6%–4% are not of endodontic origin (1, 7, 9, 10). Several different non- endodontic periapical lesions have been reported, such as odontogenic cysts and From the *School of Dentistry, University of Ribeirao Preto (UNAERP); and † Private Dental Clinic, Ribeirao Preto, Sa ˜o Paulo, Brazil. Address requests for reprints to Professor Danyel Elias da Cruz Perez, Universidade de Ribeira ˜ o Preto (UNAERP) - Servic ¸o de Patologia, Av. Costa ´ bile Romano, 2201 Ribeira ˆ nia, CEP: 14096-090, Ribeira ˜o Preto/SP, Brazil. E-mail address: perezdec2003@yahoo.com.br. 0099-2399/$0 - see front matter Copyright ª 2010 American Association of Endodontists. doi:10.1016/j.joen.2009.11.027 Case Report/Clinical Techniques 546 Ramos-Perez et al. JOE — Volume 36, Number 3, March 2010