[Malignant transformation of odontogenic cysts]

Five out of 4,172 operated maxillary cysts (3 developed within the maxillary and 2 in the mandible) presented a malignant change of epithelium. In all these 5 cases histology demonstrated a transition from normal to cancerous epithelium. The overall percentage of malignant change was of 0.12%, with 0.077% for non-keratinized epithelium lining odontogenic cysts (3 cases) and 0.65%, that is 8 times higher, for keratinized ones (2 cases). Keratinization of cystic epithelium and chronic inflammatory lesions were the main risk factors.