CC
A 68-year-old White male is referred for evaluation of “swelling of my right lower jaw.”
Dentigerous cyst
Dentigerous cysts, also known as follicular cysts, are typically associated with an impacted tooth, most commonly the mandibular third molar. It is more prevalent in White people, has a slight male predilection, and is usually seen in the age range of 10 to 30 years.
HPI
Approximately 2 months earlier, the patient noticed a nonpainful swelling of the right posterior mandible. (Dentigerous cysts can cause expansion but are typically not painful unless secondarily infected.) He was seen by the referring general dentist who had discovered a radiolucent lesion on a periapical radiograph. The patient denies any history of pain or sensory changes, drainage from the site, or trismus. He has not experienced any fevers, chills, night sweats, or unintentional weight loss.
PMHX/PDHX/medications/allergies/SH/FH
Noncontributory. There is no history of similar presentations in his family. (There is no familial predisposition.)
Examination
General. The patient is well-appearing but anxious (patients are often anxious because they fear a malignant process).
Maxillofacial. There is noticeable right lower facial swelling isolated to the lateral border of the mandible that does not extend below the inferior border. Consistent with a noninflammatory process, the mass is hard, nonfluctuant, and nontender to palpation. There are no facial or trigeminal nerve deficits. (Paresthesia of the right inferior alveolar nerve would raise the suspicion for an infiltrative or malignant process.)
Neck. The patient does not have cervical or submandibular lymphadenopathy. Lymphadenopathy would be indicative of an infectious or neoplastic etiology, so a careful neck examination is paramount in the evaluation of any head and neck pathology.
Intraoral. The occlusion is stable and reproducible. There does not appear to be displacement of the dentition in the involved area. (Dentigerous cysts do not typically alter the occlusion.) Interincisal opening is within normal limits. There is significant buccal expansion of the right mandible, extending posteriorly from the mental foramen and into the ascending ramus. (Large cysts may be associated with a painless expansion of the bone, but most are asymptomatic and do not cause expansion.) The patient does not have a palpable thrill or an audible bruit (both of which are signs of arteriovenous malformations). The oral mucosa is normal in appearance with no signs of any acute inflammatory processes.
Imaging
When evaluating intraosseous lesions of the mandible, the panoramic radiograph is an excellent initial study to assess the underlying bony and dental anatomy.
Dentigerous cysts are pericoronal lesions that attach to the cementoenamel junction of the associated tooth. However, large dentigerous cysts may radiographically encompass the roots of the impacted tooth; other pathologies may appear to be pericoronal radiolucencies on imaging. Therefore, imaging is a not a diagnostic tool for evaluation of lesions, and a histologic assessment is required for final diagnosis. When the pericoronal radiolucency of an impacted tooth is 3 mm or smaller, the tissue is deemed to be an enlarged dental follicle and can be discarded. However, when the pericoronal radiolucency of an impacted tooth is larger than 3 mm, cystic development should be considered, and tissue should be submitted for histological evaluation.
A computed tomography scan ( Fig. 2.1 ) is not essential but helps delineate the three-dimensional extent and regional architecture, including involvement of the mandibular cortices (cortical perforation is seen with some tumors and locally aggressive cysts) and the lesion’s proximity to the inferior alveolar canal.
In this patient, a panoramic radiograph ( Fig. 2.2 A) demonstrates a well-corticated unilocular radiolucent lesion of the right posterior mandible extending from the area of tooth #31 up to the sigmoid notch and coronoid process. The right mandibular third molar (tooth #32) is displaced inferiorly, and the lesion involves the roots of tooth #31 with some resorption and superior displacement of the tooth. After aspiration and incisional biopsy, teeth #31 and #32 were extracted, and the cyst was enucleated ( Fig. 2.2 B–E). Six- and 16-week postoperative panoramic imaging demonstrate good progressive bony fill of the defect ( Fig. 2.2 F and G).
Labs
No laboratory tests are indicated unless dictated by the medical history. If a brown tumor of hyperparathyroidism is on the differential diagnosis, serum calcium, phosphate, and parathyroid hormone levels should be obtained. Brown tumors are sequalae of primary hyperparathyroidism, leading to bony lesions with abundant hemorrhage and hemosiderin deposition (giving it a brown color). Removal of the hyperplastic parathyroid tissue is the definitive treatment.
Differential diagnosis
The differential diagnosis for a unilocular radiolucency includes odontogenic and non-odontogenic cysts, benign and malignant tumors, and (less commonly) vascular anomalies. In general, large radiolucencies with multiple septations should raise the suspicion for other more aggressive entities because most dentigerous cysts are small and unilocular. A recent study found that among pericoronal radiolucencies, lesion size 2 cm or larger was predictive of a nondentigerous cyst diagnosis on final pathology. The presence of loculations on presurgical imaging independently increases the risk for a nondentigerous cyst diagnosis by 12-fold. When considering possible diagnostic alternatives, the lesions presented in Box 2.1 should be considered with the first three being the most likely.
