Atypically grown large periradicular cyst affecting adjacent teeth and leading to confounding diagnosis of non-endodontic pathology.

This article reports a case of a large osteolytic lesion in the mandible, mostly associated with the apices of the premolars, and suspected as having a non-endodontic origin because the 2 premolars responded positively to the cold sensibility test. The distal border of the lesion reached the mesial root of the first molar, which also had a small lesion in its distal aspect. Cone-beam computed tomography revealed that the large lesion communicated with the small molar lesion. Because the large lesion was suspected as having a non-endodontic origin, surgery was scheduled for enucleation and biopsy. The molar was root canal-retreated, and the 2 premolars treated. Histologic analysis of the premolar pulps showed vitality but advanced degenerative changes. The lesion was histologically diagnosed as an inflammatory periradicular cyst, which originated in the first molar and had an atypical growth to the premolar area. Follow-up revealed that the affected area healed uneventfully.