Peripheral Ameloblastoma: A Study of 18 Cases and Usage of Ber-EP4 Immunohistochemistry to Rule out a Diagnosis of Intraoral Basal Cell Carcinoma.

PURPOSE: Peripheral ameloblastoma (PA) is a rare odontogenic tumor arising in the mucosa of tooth-bearing areas of the jaws that typically shows no radiographic evidence of bone involvement. It bears close histologic resemblance to intraoral basal cell carcinoma (IOBCC), an extremely rare entity. In our experience from previous published data, 3 cases of IOBCC were initially misdiagnosed as PA and were later differentiated from PA on the basis of Ber-EP4 protein expression. This unusual but significant experience set the premise for us to rule out a diagnosis of IOBCC by evaluating Ber-EP4 expression in all previously diagnosed cases of PA from the University of Florida Oral Pathology (UFOP) biopsy service archives.

MATERIALS AND METHODS: With institutional review board approval, 18 cases of PA were retrieved from the UFOP biopsy service archives. We describe the clinicopathologic features of these cases and discuss the Ber-EP4 immunohistochemical staining performed to rule out a potential diagnosis of IOBCC. In addition, we conducted calretinin and epithelial membrane antigen staining for 1 case of PA.

RESULTS: Most PAs presented in the lingual gingiva of the posterior mandible. Men were affected twice as often as women, and the average age at the diagnosis was 59 ± 21.5 years. Of the 18 lesions, 13 showed no reactivity to Ber-EP4, 4 displayed patchy membranous immunoreactivity, and 1 demonstrated nonspecific reactivity.

CONCLUSIONS: We have concluded that all cases of PA that present with histologic overlap with basal cell carcinoma, especially those from incisional biopsies, those that appear significantly infiltrative, and those that appear ulcerated and/or demonstrate recurrence should be evaluated with Ber-EP4 to rule out IOBCC.