So-called calcifying odontogenic cyst: review and discussion on the terminology and classification.

The so-called calcifying odontogenic cyst (COC) shows extensive diversity in its clinico-histopathological appearances and biological behaviour. Because of this diversity, there has been confusion and disagreement on the terminology and classification of this lesion. The attempts at classification of COC may be divided into two concepts. The first concept is the "monistic" one that all COCs are neoplastic in nature, even though the majority are cystic in architecture and appear to be non-neoplastic. The second is the "dualistic" concept that COC contains two entities: a cyst and a neoplasm. Although the World Health Organization (WHO) classified COC as an odontogenic tumour in 1992 based on the former concept, current thinking favors strongly the latter one. In this article, several previous classifications of COC in the literature are discussed and a new simple classification scheme based on the "dualistic" concept is proposed.