RESUMO
Aim: This study reports a rare case of simple bone cyst (SBC) with a radiographic behavior similar to malignancies and a mixed internal structure in a 43 year-old woman who presented to a dental office with clinical symptoms. Presentation of Case: A 43 year-old woman presented to a dental office with chief complaint of pain at left mandibular molars for almost 2 months. She was wearing a cervical collar for some spine problems. The panoramic x-ray showed a radiolucent lesion with well defined non-corticated borders in periapical region of the mandibular left first molar (tooth 36). The tooth was vital. Cone Beam Computed Tomography (CBCT) images showed a lytic lesion with well defined noncorticated borders that destructs the lingual cortical wall without any sign of expansion to soft tissues. The upper border of the mandibular canal was unclear and seemed destructed by the lesion. The internal structure of the lesion seemed mixed. Three months later, the patient reported numbness of her lower lip. CBCT showed an enlargement of the lesion and the presence of buccal cortical perforation was seen. On biopsy the lesion was diagnosed as a Simple Bone Cyst (SBC). Discussion: SBC is often a benign lesion which appears as a radiolucent lesion with scalloped corticated borders. Adversely, current case showS a mixed lesion with buccal and lingual cortical perforation and rapid growth .the concomitant pain, the lower lip numbness and the radiographic appearance suggest the probability of an aggressive local condition or a malignancy Conclusion: SBC may have various radiographic presentations, unusual SBCs (or Traumatic bone cysts TBCs) may show aggressive radiographic characters. In these cases, biopsy and pathological features are necessary for diagnosis.