Introduction
Developing odontoma replaced ameloblastic fibro-odontoma (AFO) as a new entity in the latest (4th) edition, 2017, of the World Health Organization (WHO) Head and Neck Tumors classification.1 The world health organization has classified developing odontoma as a mixed odontogenic tumor.2 It is a rare mixed odontogenic tumor characterized by the proliferation of odontogenic epithelium as cords and small islands in a background of primitive ectomesenchymal cells similar to dental papilla and in association with calcified tooth structures including enamel and dentin.3
The calcifying odontogenic cyst (COC) is a rare benign odontogenic lesion that exhibits both cystic and neoplastic features. It has a highly diverse histopathologic characteristics.4 In 1962 Gorlin described the first case of COC as a separate entity thus the frequent use of the term Gorlin cyst for this lesion.5 COC has a wide variety of clinical and histopathological manifestations and debate about the true nature of this lesion is still ongoing.4,6 Following several classifications and reclassifications, the WHO in 2005 recommended and classified it as calcifying cystic odontogenic tumor (CCOT).6 In the 2017 classification, the cystic form of the lesion was classified as a developmental cyst whereas the solid form was classified as a mixed odontogenic tumor.7
The combination of COC and Ameloblastic fibro-odontoma has been reported before. However this combination is extremely rare. This paper reports the first case of developing odontoma as a new entity arising from calcifying odontogenic cyst.