A Keratocyst in the Buccal Mucosa with the Features of Keratocystic Odontogenic Tumor
A 74-year-old man consulted our clinic with a complaint of swelling in the right buccal region. The patient noticed the swelling 5 years ago and had received aspiration therapy repeatedly to reduce the swelling. He was generally healthy and had no medical history. On examination, an elastic firm, movable mass of 50mm was palpable in the right buccal region (Fig. ). The overlying mucous membrane was normal.\nThe mass was not adhesive to either the mucous membrane or the skin. The maxilla was totally edentulous and only bilateral canines and the left first premolar were present in the mandible. Hypoesthesia or palsy of the right face, trismus, swelling of cervical lymph nodes or the right parotid gland was not observed. CT examination revealed a well-circumscribed oval cystic lesion of 35 mm with the density slightly less than that of muscle in the anterior region of the masseter muscle (Fig. ). On MRI, the lesion showed a low signal on the T1-weighted image and a heterogeneous high signal on the T2-weighted image including intermediate signal in the under portion (Fig. ). Aspiration through the buccal skin revealed whitish liquid with squamous cells and shadow cells with a few neutrophils and lymphocytes in the cytological examination.\nThe clinical diagnosis of epidermoid cyst at the right buccal mucosa was made. The lesion was intraorally extirpated under general anesthesia through the incision along the anterior border of the mandibular ramus (Fig. ). Detachment of the lesion from the surrounding tissue was relatively easy. Stensen’s duct was not related to the lesion. The wound was closed after placing a silicon drain. Wound healing is good and no sign of recurrence has been observed for more than 4 years after the surgery.\nThe lesion was cystic, 30 × 25mm, weighed about 6g and contained brown serous liquid with a few cellular debris or keratin scale (Fig. ). Histologically, the lesion was lined with squamous epithelium with parakeratinization corrugated on the surface (Fig. ). The basal layer consisted of cuboidal cells showing palisading of the nuclei and a smooth border (Fig. ). No daughter cysts, epithelial islands, hair