2. Case story / examination
A 15-year-old girl with a chief complaint of swelling in the right mandibular premolar region was referred to our department. She had a history of surgery for a congenital ear fistula. The patient first recognized a painless mass in her mandible at 6 years of age. On this occasion, she was referred to a local dental clinic for the treatment of dental caries and then to our hospital for the treatment of the mandibular tumor. Intraoral examination revealed a well-defined, painless, elastic hard mass, measuring 17×17 mm in size, between the right mandibular canine and first premolar (Figure 1). Panoramic radiography showed a radiolucent area in the alveolar bone at the same location (Figure 2). In addition, sandy calcification was observed inside the lesion. Computed tomography (CT) revealed compressive bone resorption of the alveolar bone between the mandibular right canine and first premolar (Figure 3). Magnetic resonance imaging (MRI) revealed an endophytic appearance of a well-defined enhancing mass on the right side of the mandible on T2-weighted imaging (Figure 4).
A biopsy was performed under local anesthesia and a benign tumor with fibroblast proliferation was diagnosed. Tumor resection was performed under general anesthesia. The tumor was detached from the surrounding bone surface and resected, including the periosteum. A bone depression was observed around the tumor, and the bone surface was smooth. The tumor was 17×17 mm in size and had a smooth surface. Histopathological examination revealed spindle-shaped fibroblast-like cells that spread subcutaneously. Scattered cord-like and lump-like epithelial components were observed in the fibrous tissue near the base of the tumor (Figure 5A). No atypical cells or nuclear fission were observed. Cementum-or bone-like calcifications were observed in the deep area of the tumor. Epithelial components resembled Marasse’s remaining epithelial or Hertwig epithelial sheath and were positive for cytokeratin (CK) CK19 staining (Figure 5B, C). There were no signs of post-operative recurrence after 16 months.