Primary intraosseous carcinoma arising in a mandibular cyst.

Although primary intraosseous carcinoma of the mandible is an uncommon lesion, they may not be as rare as generally believed. These tumours may, in theory, arise de novo from odontogenic remnants or from the malignant transformation of the lining of odontogenic cysts or tumours. Diagnosis based on histology and radiology is difficult. The prognosis is more favorable when PIOCs arise from odontogenic cysts. These tumors are locally aggressive and metastasize to regional nodes. The case study of a 70 year-old man with a primary intraosseous squamous carcinoma arising from a mandibular cyst is given.