Keratocystic odontogenic tumor: a retrospective study of 183 cases.

In 2005, the WHO Working Group considered odontogenic keratocyst (OKC) to be a tumor and recommended the term keratocystic odontogenic tumor (KCOT), separating the lesion from the orthokeratinizing variant, which is now considered an odontogenic cyst. We analyzed the clinicopathological features of KCOTs encountered over a period of 28 years at Meikai University Hospital. The diagnosis was confirmed by reevaluation of hematoxylin and eosin-stained slides on the basis of the 2005 WHO Classification. Clinical history was also taken into consideration. A total of 183 KCOTs were found, and the two genders were affected almost evenly (51.3% male; 48.7% female; male to female ratio 1.05 to 1). Patient age at the time of diagnosis ranged from 6 to 78 years, with a peak in the third decade of life (mean age: 32.8 years). The mandible was the site of occurrence of 70.5% of tumors; 16.4% occurred in the maxilla and 13.1% in both. Association with the nevoid basal cell carcinoma syndrome (NBCCS) was found in 6.0% of all tumors, and recurrence was found in 13.1% of patients. We found that tumors that initially appeared in the maxilla alone had a higher recurrence rate than those that first appeared in the mandible alone. Pathological examination of KCOT is important to avoid misdiagnosis and provide appropriate treatment and follow-up.