Case report
A 17 year-old female was referred to the Oral and Maxillofacial Pathology Department, Tehran University of Medical Sciences, Tehran, Iran, for consultation and diagnosis of a lesion on the right side of her mandible. The previous histopathologic diagnosis of the lesion was ameloblastoma. Before the incisional biopsy, the patient’s chief complaint was a swelling in the right posterior mandible for 2 weeks. There was no facial asymmetry. In the intraoral examination, a slight swelling was observed in the right retromolar area. The swelling was non-tender and was firm in consistency. Panoramic and CBCT radiographs showed a well-defined radiolucent lesion that contained areas of radiopacity around the crown of an unerupted third molar. The margins of the lesion were sclerotic (Figure 1)
In the review of the microscopic slides, a cystic lesion lined by an odontogenic epithelium which consists of cuboidal to columnar basal cells with hyperchromatic nuclei demonstrating reverse polarity was observed. The superficial epithelial cells were loosely arranged and resembled the stellate reticulum of enamel organ. Aggregations of ghost cells were notable within the epithelium (figure 2A). Sections of numerous tooth-germ structures consisting of nests and islands of enamel organ and dental papilla were also evident in the cyst wall. In some areas, tooth buds appeared to originate from the cystic epithelium (figure 2B). There were also sections of developed tooth structures consists of mature enamel cap and tubular dentine (figure 3). Area of ectomesenchyme-like cell proliferation similar to dental papilla were also seen. Based on these histopathologic findings the diagnosis was developing odontoma arising from a calcifying odontogenic cyst. The lesion was treated by conservative excision and there was no recurrence after one-year follow-up (figure 4).