CC
A 38-year-old female is referred for evaluation of a mandibular lesion. She states, “I have a tumor in my lower jaw.”
Cemento-ossifying fibroma
In the most recent World Health Organization (WHO) 2022 classification, cemento-ossifying fibroma (COF) is a neoplasm under odontogenic tumors of mesenchymal origin. The word cementum in COF is used to emphasize on its odontogenic origin because it suggestively arises from the periodontal tissue. Accordingly, COF mostly occurs in tooth-bearing areas with the mandible being the most affected arch, particularly the premolar–molar region. COFs are reported to have a distinct female predilection and tend to occur in the second to fourth decades of life.
HPI
Approximately 3 years earlier, the patient noticed a painless bony expansion in the posterior mandible. (COF is usually a painless, slow-growing lesion of gnathic occurrence consistent with the posterior mandibular arch.) The patient stated that the swelling had been slowly enlarging over the past 3 years and that she was previously scared to seek treatment. As the mass enlarged, it started to interfere with function (chewing and talking), so the patient was encouraged to pursue treatment. (COFs that are left untreated can become very large.)
PMHX/PDHX/medications/allergies/SH/FH
Noncontributory.
Examination
General. The patient is well developed and well nourished and in no apparent distress.
Maxillofacial. There is a noticeable enlargement of the posterior mandible. A firm, bony mass is palpable extending from the distal aspect of the lower left second premolar till the mesial aspect of the lower left second molar. The mass has expanded the buccal and inferior cortices. (“Downward bowing” is common in large ossifying fibromas of the mandible.) Sensory examination shows that the mental nerve distributions are intact bilaterally. (Perineural invasion is not seen with ossifying fibroma.)
Neck. No lymphadenopathy is noted. (Cervical lymphadenopathy is not seen in benign neoplastic processes.)
Intraoral. There is a considerable amount of bony expansion, more evident on the buccal aspect of the posterior mandible, causing lingual displacement of the posterior teeth and encroaching on the tongue space ( Fig. 5.1 ). (Larger lesions may cause tooth displacement and root divergence, resorption, or both.) The overlying attached gingiva and mucosa are normal in appearance. (Mucosal ulcerations can be a sign of a malignant process; however, traumatic ulcerations can occur within large, expansible, benign lesions.)
Imaging
A panoramic radiograph is a good initial screening. It does provide an overview of the bony anatomy and architecture of the maxilla and mandible. Osseous lesions are well characterized on a panoramic film, allowing the clinician to make a working differential diagnosis based on the lesion’s location, radiodensity, locular or trabecular pattern, border demarcation, size, and effect on adjacent structures (i.e., root resorption, root divergence, scalloping, cortical expansion, cortical erosion, or destruction). However, it lacks the buccolingual dimension and may be influenced by magnification or distortion, as well as superimposition. This is why cone-beam computed tomography (CBCT) is the imaging modality of choice in this case to accurately assess the extent of buccal and lingual expansion and provide accurate measurements of the lesion’s size and extensions, as well as the relation to vital structures (which is the inferior alveolar canal [IAC] in this particular case). CBCT is exceedingly common in the office and offers a great deal of information regarding the nature of the mass. However, when there are radiographic signs of a malignant process (e.g., poorly defined radiolucency, mottled or “moth-eaten” appearance, unilateral widening of the periodontal ligament space, floating teeth, cortical perforation, or “spiked roots”), CT of the neck is also required to assess the nodal involvement, which can help in tumor staging and indicate if there are any extensions into the surrounding soft tissue. CT provides additional information (e.g., lingual or buccal cortex thinning or perforation, location of the IAC) and is especially useful when the lesion is difficult to assess on plain films. A three-dimensional printed stereolithographic model is useful to prebend a reconstruction plate in anticipation of resection. It can also be used in surgery simulation and practice, identification of the incision lines, and osteotomy planes. This helps decreasing the surgery time and maximizing the patient’s standard of care.
The internal structure of ossifying fibroma varies, depending on the degree of maturity of the lesion. Early ossifying fibromas are radiolucent, typically encapsulated at this point because they enlarge in bone, and as they mature, they become mixed radiolucent–radiopaque and may eventually become predominantly radiopaque. Untreated, these tumors are likely to reach large proportions as they continue to grow. When the tumors become larger, they lose their encapsulation and invade for a few millimeters.
In this patient, the CBCT-reconstructed panorama, sagittal, and serial cross-sectional images show a well-defined unilocular mixed hyper- and hypodense lesion (predominantly hyperdense with radiodensity close to that of teeth). The lesion extends mesiodistally from the distal aspect of the lower left second premolar to the mesial aspect of the lower left second molar and occlusogingivally from the alveolar crest to near the inferior mandibular cortex. A radiolucent rim more expressed in the sagittal cut separates the lesion from the surrounding bone. The lesion causes concentric buccolingual expansion favoring the buccal cortex and causing thinning of both cortices. There is also an evident downward displacement in the IAC ( Figs. 5.2 and 5.3 ).
Labs
There is one reported case in the literature that showed markedly high levels of serum parathyroid hormone. The exact reason was not mentioned in the reported case; we suggest that it may related to the osseous calcifications.
Baseline hemoglobin and hematocrit levels can be obtained before tumor resection. No other laboratory tests are indicated unless dictated by the medical history.
Differential diagnosis
The differential diagnosis of COF includes mainly the mixed radiolucent–radiopaque lesions. However, it is often challenging to differentiate COF, particularly from fibrous dysplasia (FD). Radiologic assessment plays a viable role in differentiation, in which COF shows more concentric expansion with a clear epicenter, but FD has a fusiform to oval pattern of expansion. On the other hand, COF can be separated from the surrounding bone “shell out”; on the contrary, FD tends to have a blending outline. Additionally, the internal structure and degree of mineralization are more heterogenous in COF, in which FD shows a more homogenous pattern throughout the lesion. Regarding the effect on surrounding vital structures, whereas COF causes downward displacement of the IAC, FD causes a pathognomonic upward displacement. Another challenge is differentiating COF from cemento-osseous dysplasia (COD) because they can be histologically indistinguishable. The unifocal, regular pattern of COF is a radiologic key of differentiation in which COD tends to be multifocal, irregular in appearance, and considered as an incidental finding. Occasionally, cementoblastoma can be also considered, in which cementum has limitless capability of proliferation; however, radiologically, cementoblastoma mainly tends to obscure the root. Several mixed radiolucent–radiopaque lesions other than an ossifying fibroma are listed in Box 5.1 .
