Correlative X-ray, CT and histopathology findings of a mandibular cementoblastoma

A 19-year-old female patient presented to the dental department with a one-year history of a painless, progressive swelling in the left mandibular region causing facial asymmetry. There was no history of trauma or fever. No caries were noted in the adjacent teeth.

The orthopantomogram (OPG) revealed a well-defined, circumscribed, predominantly radiopaque, mixed-density mass expanding from the mesial and distal roots of the first mandibular molar and mesial root of the second mandibular molar on the left side. A characteristic radiolucent rim continuous with the periodontal ligament is present (Figure 1).

A computed tomography (CT) scan exhibited a well-defined sclerotic mass lesion with a surrounding low attenuating halo, in contact with the roots of the 1st and 2nd mandibular molars on the left side causing partial resorption of the root of the first molar (Figures 2a, 2b and 2c). It measured about 2.5 x 2.7 x 2.5 cm (CC x AP x ML).

The patient was managed by surgical resection of the mass with extraction of the involved left lower first and second molars (Figure 3). Histopathological findings of the excised specimen confirmed the diagnosis of cementoblastoma (Figures 4a and 4b).

Background

Cementoblastoma is a rare odontogenic benign tumour characterised by the deposition of calcified cementum-like tissue at the tooth root by neoplastic cementoblasts [1,2]. It accounts for less than 1% to 6.2% of all odontogenic tumours [3].

Clinical Perspective

Cementoblastoma typically occurs in young individuals under 25 years of age [4]. It is typically observed in the posterior mandible, commonly involving the molars and premolars, with the first permanent molar being the most frequently involved, with rare occurrences in the anterior mandible, deciduous tooth or maxilla [4,5]. The associated tooth is vital in about 80% of the cases. It is slow-growing and can be painful or asymptomatic [4].

Cementoblastoma shares histopathological similarities with osteoblastoma. Recent molecular studies observed that cementoblastoma exhibits FOS gene rearrangements similar to osteoblastoma, suggesting that both these conditions belong to parts of the spectrum of the same disease [6].

Imaging Perspective

On imaging, cementoblastoma characteristically manifests as a well-defined radiopaque lesion directly attached to the tooth root and circumscribed by a radiolucent rim. There is resorption of the associated root [7]. The radiolucent rim is caused by actively growing peripheral regions that lack mineralisation [8].

There are several periapical radiopaque lesions resembling cementoblastoma, including hypercementosis, periapical cemento-osseous dysplasia and condensing osteitis. Each of these conditions has distinct characteristics differentiating them from cementoblastoma.

Hypercementosis presents as irregular radiopacity around the root, distorting the normal root shape and making it club-shaped. There is no surrounding radiolucent rim [7,9].

Periapical cemento-osseous dysplasia, depending on its stage, can appear as a radiopaque lesion attached to the tooth root with a surrounding radiolucent rim. However, it typically occurs in the anterior mandible in middle-aged individuals [7,9].

Condensing osteitis appears as a radiopaque lesion without a surrounding radiolucent rim, and, unlike cementoblastoma, it is associated with a non-vital tooth, usually having a large caries [7,9].

Outcome

Tumour excision and extraction of the associated teeth is the treatment approach. When completely excised without any residual mass, the recurrence rate is low [7,10].

Take Home Message

Periapical radiopaque lesions in the mandible have various differentials. Consideration of both clinical history and radiological features is crucial as these lesions can sometimes appear quite similar. The presence of a radiolucent rim, the typical occurrence in a young patient and the association with a vital tooth are key features indicative of cementoblastoma.

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