This is a case report on a solid variant of keratocystic odontogenic tumor arising in the mandible, which aggressively infiltrated into the cancelous spaces and involved the periosteal connective tissue of the mandible. The patient was a 57-year-old woman with an ill-defined radiolucent lesion having a moth-eaten pattern in the left molar region of the mandible. Computed tomography scans revealed that the tumor penetrated the buccal cortical plate of the mandible. Histologically, the lesion was characterized by multicystic spaces lined with a thin layer of keratinizing squamous epithelium, which contained basal cells with palisaded hyperchromatic nuclei. Lumina were filled with concentric layers of parakeratin. An additional feature was the appearance of a conspicuous clear cell component showing intraluminal papillary proliferation or forming small cord-like nests in the fibrous stroma. The patient underwent segmental mandibulectomy followed by reconstruction using a titanium plate. A 20-year follow-up revealed no recurrence of the tumor.