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.