A Rare Large Residual Cyst of the Mandible

Introduction: A residual cyst is a periapical cyst persisted after its associated tooth had been extracted. Case Presentation: A ۵۹-year-old Iranian man complaining of a dull pain in his left side of the mandible after falling down one month ago was referred to the department of oral and maxillofacial pathology, Hamadan University of Medical Sciences, Iran. Panoramic film revealed a radiolucent lesion and fracture of the mandible at the right side. An excisional biopsy was obtained. Based on the histopathologic findings, residual cyst was diagnosed. Conclusions: We reported a rare case of large residual cyst. Dental practitioners should consider this lesion in the differential diagnosis of radiolucent lesions of the jaw bone.