Cell proliferation activity is high immediately above basal cells in odontogenic keratocysts and can be assosiated with epithelial dysplasia. Odontogenic keratocysts can also destroy cortical bone and expand into the surrounding soft tissues, increasing the risk of recurrence. Therefore, odontogenic keratocysts were classified as keratocystic odontogenic tumors (KCOT), excluding cases with normal epithelial keratinization, in the revised classification of odontogenic tumors established by the WHO in 2005.
The recurrence rate of KCOT has been reported to be 12 % to 63 %, with a mean value of 23 %. Various reasons for the high recurrence rate have been reported. If KCOT invades and resorbs the cortical bone of the jaw, resection of soft tissue in contact with the lesion is recommended, because tumor cells may remain in the surrounding soft tissue after resection of the bone. However, the recurrence of KCOT from residual tumor cells in soft tissue has not been reported.
We describe a patient with recurrent KCOT that arose on an autogenous iliac bone graft following segmental resection of the mandible and iliac bone grafting for reconstruction of mandible. This case emphasizes the importance of treating the tissue surrounding KCOT at the time of resection.
