Osteoid Osteoma of the Mandible – Clinical and Histological Findings

Case Report and Results

History. A healthy 18-year-old male patient presented to a private practice for oral and maxillofacial surgery in spring 2018 due to persistent and non-specific, particularly nocturnal pain, alleviated by NSAIDs. The pain was located in the right lower jaw, non-radiating and of dull quality. The patient had first noticed this pain, severe and intermittent, aggravated by palpation, a few months earlier. The initial panoramic dental radiograph showed retained teeth 18, 28 and 48 (Figure 1A). An additional dental CT indicated an unclear tumor mass near the mesial root of tooth 46 extending 0.9×0.8×0.5 cm³ (Figure 1B-D). Due to this unclear tumor mass and in combination with the reported pain, the wisdom teeth were extracted and an additional biopsy of the region of interest was made. The oral mucosa above the tumor mass appeared clearly reddened. The resection specimen showed woven bone trabeculae covered by enlarged osteoblasts and multinucleated osteoclasts and embedded in fibrous stroma containing dilated blood vessels (Figure 2A and B). From this, the histopathologic diagnosis of OO was concluded.

Physical examination. With this diagnosis, the patient was referred to the University Medical Center Hamburg-Eppendorf, Germany. On clinical examination, a scar of the lingual mandibular mucosa was noticeable several weeks after probe incision in the lower right molar region. The intact overlying mucosa did not raise suspicion for inflammation, redness or swelling. The tooth 46 was not found to be sensitive to percussion, not mobile and dental pulp testing was positive, as were the adjacent teeth. Cervical lymph nodes were not enlarged or tender to palpation. An additional finding was a movable swelling of firm elastic consistency in the central parietal region of the head. The patient was unaware of the course of progression, as this was not causing any pain or discomfort.

Diagnosis and treatment. A panoramic radiograph taken prior to the initial biopsy indicated an inhomogeneous translucency in the first molar region of the lower right jaw (Figure 3A). An additional cone beam CT with increased bone resolution and greater overview revealed a nidus with a diameter of 7.6 mm (Figure 3 A-D). Both the cone beam CT and the previously performed dental CT showed a central zone of a radiodense mineralized tissue that was distinguishable from a peripheral zone of radiolucency, again surrounded by a zone of dense sclerotic bone.

After completion of diagnosis the patient underwent general anesthesia to have the benign osseous tumor surgically removed, with simultaneous excision of the parietal formation. To this end, an incision of the lingual mucosa was made from tooth 43 to 47. A mucoperiosteal flap was formed. After subperiosteal preparation, an osteotomy in the region of 45-46 was done with a dental drill. After visualization of the spongy bone tumor it was removed by excochleation. The immediately adjacent inferior alveolar nerve as well as the mesial root of tooth 46 were preserved. Bone wax was instilled to facilitate hemostasis and healing of the bony defect. The mucoperiosteal flap was readapted and the wound defect thoroughly closed. The parietal tumor was resected by spindle-shaped incision in full depth to the epicranial aponeurosis. After thorough hemostasis the wound defect was primarily closed.

Histologic findings. During the course of the surgery, two specimens were fixed in buffered formalin and sent for histopathological evaluation. Following an EDTA-decalcification of the surgical specimen (maximum diameter 0.8 cm), a subsequent histological analysis confirmed the diagnosis of OO. The tumor harvested intraorally consisted of structurally disorganized woven bone with non-mineralized osteoid and prominent vasculature (Figure 4A). A central zone of osteosclerosis could be distinguished from a peripheral zone with less mature cells and little matrix-formation. The cells were characterized by an osteoblastic disorganized overgrowth with the formation of immature bone as well as scattered multinucleated osteoclasts (Figure 4B). The tumor had formed a fibroblastic pseudo capsule. No signs of malignancy were noted. Measurements were 0.8x0.5x0.5cm. The parietal tumor was found to be a regressive pilomatrixoma, excised in toto (not shown). Measurements were 1.6×0.5×1.0 cm³.

Follow-up. After quick recovery and an uneventful course, the patient was discharged from the hospital on post-operative day one. The panoramic radiograph taken post-operatively showed no signs of fracture, dental damage or displacement. Furthermore, there were no signs of a remaining tumor mass (Figure 5A). The patient presented to our outpatient clinic three months after surgery. An additional cone beam CT confirmed the complete removal of the tumor (Figure 5B-D). The intraoral wound healing showed good consolidation. Teeth 45, 46 which were immediately adjacent to the OO showed no signs of mobility, pulp test was positive. The patient was completely pain-free and adhering to regular follow-up.