The glandular odontogenic cyst (GOC) is a rare pathology of odontogenic origin, which can behave unpredictably. It is problematic in clinical, radiographic and histological diagnostics. Intraosseous mucoepidermoid carcinoma (MEC) is a rare tumor which affects the jaws, typically found in the mandible. This malignancy, which usually originates from the salivary glands, can also be caused by a transformation of the mucous cells found in odontogenic cysts. This article presents a rare case of GOC transforming into MEC of the mandible, which was reported during the treatment of a 52-year-old male patient. The aim of this work was to present some of the therapeutic and clinical difficulties encountered when GOC transforms into mucoepidermoid cancer in the mandible, considering the pathomorphological and histological differentiations. The differentiation between MEC and GOC might be difficult through microscopic examination and requires the cooperation of a clinician-a maxillofacial surgeon-and a histo pathologist.