This 25 year old male patient presented with an 16 month history of an asymptomatic swelling in the anterior mandible. At this moment, we are puncturing the lesion. We can observe the emptying out (cystic fluid) and the anterior teeth moving. After an incisional biopsy the diagnostic was calcifying cystic odontogenic tumor (CCOT). This pathology also known as calcifying odontogenic cyst (COC) or Gorlin cyst is a rare developmental lesion which arises from odontogenic epithelium. Unfortunately, the next step will be the mandibular resection due to the extension of the lesion, which already affects the entire inferior border of the mandible.