Keratocystic odontogenic tumour (KCOT) misdiagnosed as a dentigerous cyst

Keratocystic odontogenic tumours are known for their peculiar behaviour, varied origin, debated development, unique tendency to recur and disputed treatment modalities. Thus, it has been the subject of much research over the last 40 years. It was formerly known as odontogenic keratocyst (OKC). OKC received its new title as keratocystic odontogenic tumour (KCOT) by the WHO (2005) in order to suggest its aggressive and recurrent nature. KCOT is a benign intraosseous neoplasm of the jaw. Involvement of the maxillary sinus is an unusual presentation. We present the case of an 11-year-old child with extensive KCOT and an impacted canine in the right maxillary sinus. The cyst was initially misdiagnosed to be a dentigerous cyst based on the clinical and radiographic features though a differential diagnosis of KCOT and adenomatoid odontogenic tumour was made. The histological examination of the specimen finally confirmed it to be a KCOT. The clinical, radiological and histological features of this tumour along with its surgical management have been discussed.