A nineteen years old male patient showed a cystic lesion in left maxillary canine to premolar area (#23-#25). This lesion was asymptomatic, and found during his routine radiological check in local clinic. In the radiological observation the cystic lesion showed round radiolucent image containing many calcified bodies which were usually small but irregular in shape, expanding tumorously and resulted in the displacement of canine and second premolar in the absence of first premolar. The lesion was surgically enucleated, and a cystic fibrous tissue containing abnormal teeth was removed and examined pathologically. With the histological observation of tumorous odontogenic epithelium including many ghost cells, which were closely associated with abortive teeth, the lesion was finally diagnosed as CCOT associated with complex odontoma. The ghost cells of CCOT was strongly positive for β-catenin, GADD45, and LC3, and slightly positive for MMP-9, while they were rarely positive for BCL2, Wnt1, HSP-70, and p38. Therefore, it was presumed that the ghost cells of CCOT might undergo dormant cell state through altered cytodifferentiation stimulated by severe growth arrest, DNA damage signaling, and abundant autophage formation.

Although the mechanism of the abnormal calcification in the calcifying odontogenic cyst (COC) was not elucidated so far, it has been known that the ghost cells are closely related to the calcification, producing dystrophic globular cementum-like materials, comparable to pilomatricoma in epithelium1). Here, we presented a case of COC occurred in left maxillary canine area of 23 years old female, exhibiting a collection of aberrant ossification admixed with basophilic ghost cells in comparison with seven cases of COC. In the polarizing microscope observation with Masson trichrome stain the present case clearly disclosed the typical birefringence of bony tissue, stained red in von Gieson stain, indicating the collagenous backbone. Some ghost cells showed the features of interdigitating epithelial attachments, empty spaces of nuclei, and reticular basophilic cytoplasms, which were similar to the basophilic ghost cells of philomatricoma. The present case demonstrated the aberrant ossification by basophilic ghost cells in COC similar to the ossification of pilomatricoma