CASE REPORT Unicystic ameloblastoma: a possible pitfall in periapical diagnosis E. M. Cunha 1 , A. V. Fernandes 1 , M. A. Versiani 2 & A. M. Loyola 1 1 Department of Pathology, Dental School, Federal University of Uberla ˆ ndia; and 2 Department of Endodontics, Brazilian Association of Dentistry, Uberla ˆ ndia, Brazil Abstract Cunha EM, Fernandes AV, Versiani MA, Loyola AM. Unicystic ameloblastoma: a possible pitfall in periapical diagnosis. International Endodontic Journal, 38, 334–340, 2005. Aim To report a clinical case of unicystic ameloblastoma previously misdiagnosed as radicular cyst. Summary A 49-year-old white male was referred to a private practitioner complaining of an asymptomatic bony hard swelling of the left posterior mandible. The patient’s dental history indicated that his left mandibular first molar had been extracted approximately 10 years previously. At that time, preoperative radiographic examination demonstrated a radiolucent area of 1.5 cm diameter with well-defined margins involving the distal root of tooth 36. The lesion was diagnosed as cystic and surgery for its removal was advised, but not performed. At presentation, radiography demonstrated a well-defined 3 cm diameter radiolucency extending from the second premolar to the second molar. The lesion was enucleated and histopathological examination confirmed a diagnosis of unicystic amelob- lastoma. Key learning points • Despite a clinical diagnosis of periapical disease of endodontic origin, a nonendodontic lesion may be present. • Unicystic ameloblastoma located on the periapical area of a tooth can lead to a pulp- periapical misdiagnosis, and should be considered in differential diagnosis. • All tissue specimens recovered in apical surgery should be submitted to histopatho- logical analysis. Keywords: ameloblastoma, diagnosis, odontogenic tumours, periapical diseases. Received 26 April 2004; accepted 8 February 2005 Introduction Ameloblastoma is an aggressive but benign epithelial neoplasm of odontogenic origin (Small & Waldron 1955, Hollows et al. 2000, Ord et al. 2002). Robinson & Martinez (1977) were the first to describe a distinct variant of ameloblastoma that was referred to as Correspondence: Prof. Adriano Mota Loyola, Universidade Federal de Uberla ˆ ndia, Laborato ´ rio de Patologia, Av. Para ´, 1720 – Hospital das Clı ´nicas, CEP 38.405-900, Uberla ˆ ndia (MG), Brazil (Tel.: +55 (0)34 3218 2263; fax: +55(0) 34321 82626; e-mail: adrianol@hc.ufu.br). International Endodontic Journal, 38, 334–340, 2005 ª 2005 International Endodontic Journal 334