[Late recurrence of keratocystic odontogenic tumor. A report of three cases].

Background: Keratocystic odontogenic tumours (KCOT) are benign neoplasia of dentogenic origin and have a high relapse rate. Various invasive treatment methods (decompression, marsupialisation, enucleation, enucleation with adjunctive therapy such as scraping out of the bone cavity, Carnoy's solution or cryotherapy, mandibular resection) have been described for the treatment of KCOT. There is no common opinion on the best kind of treatment. Most of the articles in the literature report on a follow-up period of 5-7 years, but relapses have been described even after longer periods of time. This article presents 3 cases with late relapses that were treated at the University of Zurich, Center of Dental Medicine, Clinic of Cranio-Maxillofacial Surgery and Clinic for Oral Surgery. At the time of the initial diagnosis, the patients were 19, 24.5 and 36 years old. In all 3 patients the KCOT was localized in the angulus/ramus mandibula and an impacted wisdom tooth was present in the affected area. Case no. 1 was treated solely by marsupialisation of the KCOT. In cases no. 2 and 3, the cystic lesion was first marsupialised and later treated by enucleation and application of Carnoy's solution. In case no. 1, a relapse developed 13.5 years after the first operation. In case no. 2, relapses occurred 9, 28 and 31 years after the first operation. In case no. 3, a first relapse appeared 9 years and a second one 18 years after the first operation.

Conclusion: Patients with a KCOT require lifelong aftercare because relapses of KCOTs can arise even after 10 or more years. The aftercare concept at the University of Zurich, Center of Dental Medicine, Clinic of Cranio-Maxillofacial Surgery and Clinic for Oral Surgery therefore consists of a clinical and x-ray (orthopantomogram) follow-up examination every year for the first 10 years and every two years thereafter.