J Oral Maxillofac Surg 49:97&974. 1991 Peripheral Ameloblastoma: A Clinical and Histologic Study of I I Cases SAMIR K. EL-MOFTY, DMD, PHD,* NICHOLAS 0. GERARD, DMD,t SAM E. FARISH, DMD,$ AND BRAD RODU, DDS§ Peripheral ameloblastoma (PA) is a rare odontogenic tumor. Previously, only 39 cases of PA had been reported in the English literature. In this article 11 additional cases of PA are presented. Concordance with previ- ous cases was evident with regard to race, clinical appearance, and site of predilection. However, differences were observed with regard to age, sex distribution, and predominant histologic pattern. The average age in the current cases is younger, there is no male bias, and the most common histologic pattern is plexiform rather than follicular or acanthomatous. Recurrence following simple excision is rare, but has been reported. Long- term postoperative follow-up is recommended. Peripheral ameloblastoma (PA), also known as extraosseous or soft tissue ameloblastoma, is a rel- atively uncommon odontogenic tumor that is histo- logically identical to the classic intraosseous amelo- blastoma. Almost all previously reported cases of PA were published as single case reports. In a com- prehensive review of the English language literature in 1987, Buchner and Sciubba’ reviewed 32 well- documented cases, and since then three additional cases have been reported.2-4 In a study of 116 cases of ameloblastoma, Waldron and El-Mofty’ found that 5% were peripheral. In nearly all of the re- ported cases of PA, the tumor developed in the soft tissue overlying the alveolar bone. The occurrence of PA in other sites in the oral cavity has been re- ported in only four cases, three of which were on the buccal mucosa,6-8 and one of which was in the floor of the mouth.’ The term basal cell carcinoma * Professor of Oral Pathology, Department of Pathology, Washington University, School of Medicine, St Louis. t Resident in Oral and Maxillofacial Surgery, Vanderbilt Uni- - . versity, Nashville, TN. $ Staff Oral and Maxillofacial Sureeon. Deoartment of Veter- I . ans Affairs Medical Center, St Louis. § Associate Professor, Oral Pathology, Department of Diag- nostic Studies, University of Alabama School of Dentistry, Bir- mingham, AL. Address correspondence and reprint requests to Dr El-Mofty: Washington University School of Medicine, Division of Surgical Pathology, Oral Pathology Section, One Barnes Hospital Plaza, St Louis, MO 63110. 0 1991 American Association of Oral and Maxillofacial Sur- geons 0278-2391/91/4909-0008$3.00/O of the oral cavity has occasionally been used to de- scribe PA. ‘.‘“-‘4 According to some authorities,15*‘6 this is a matter of semantics and the two lesions are the same. The purpose of this article is to review the clinical and histologic findings in 11 previously unpublished cases of PA and to compare our findings with those in the 39 published cases. Materials and Methods Ten cases of PA were obtained from the tiles of Washington University School of Dental Medicine, which also contained cases from other oral pathol- ogy services received as part of an ongoing slide exchange-peer review program. Case number 11 was received from the St Louis VA Medical Center. In all cases received from other oral pathology ser- vices, there was complete concurrence with the di- agnosis of the contributor. Results The demographic, clinical, and histologic findings in the I1 cases are summarized in Table 1. The age of the patients was known in 10 of the cases and ranged from 33 to 68 years; the average age was 47 years. Half of the cases occurred in the fourth de- cade, while the other half affected patients in their fifth decade and older. In the 10 cases where gender was known, the male to female ratio was 1: 1. Seven tumors (64%) occurred in the mandible, 4 970