An incidental unilocular radiolucency of the mandibular angle and an opaque maxillary sinus

Ranked differential:

1. Dentigerous cyst - most likely. It is well corticated, unilocular, and attached at the cementoenamel junction of an impacted tooth, with the crown enveloped by the lesion. This is the classical description and by far the commonest pathology of this kind around an impacted third molar.
2. Odontogenic keratocyst (OKC) - plausible. OKCs are often less well corticated, scalloped, and grow along the medullary cavity with minimal expansion, but they can look identical to a dentigerous cyst around an impacted tooth. The distinction matters because recurrence rates differ markedly.
3. Unicystic ameloblastoma - less likely but must be on the list; would be expected to show more expansion, root resorption and a more irregular margin, and is more common in a younger age group.
4. Ameloblastoma (multilocular) - unlikely given the unilocular, corticated appearance with no expansion.
5. Inflammatory or hyperplastic follicle / radicular cyst - the follicle around an impacted third molar is normally <3 mm; 20 mm is far too large. A radicular cyst would need a necrotic tooth as the source, which is not described.

Immediate next steps:

• Take a periapical view of the area to assess cortication, the relationship to the canal and any root resorption - the panoramic image distorts this region.
• CBCT to define the true extent, the relationship to the inferior alveolar canal and lingual cortex, and the effect on the roots of 37. This changes the surgical plan and the consent discussion.
• Assess sensation in the lower lip and chin and record it before any surgery.
• Routine blood tests are not needed; the diagnosis is not made radiographically.

Key point: the only way to distinguish these entities is histopathology of the excised specimen. No radiographic interpretation should be presented to the patient as a diagnosis.

General principle: enucleation of the lesion together with removal of the associated impacted 38, and submission of the entire specimen for histopathology.

Why remove the tooth: the cyst is attached to the tooth, the third molar is non-functional, and leaving it behind risks recurrence and makes complete removal of the lining impossible.

Marsupialisation would be preferred if:

• the lesion were very large, with a high risk of pathological fracture of the angle if enucleated in one stage;
• the lesion closely involved the inferior alveolar nerve, so that enucleation risked permanent paraesthesia;
• the patient were medically unfit for a longer procedure, or very young with developing dentition where preserving adjacent tooth germs matters. Marsupialisation decompresses the lesion and allows bone to fill in, with definitive enucleation at a second stage if needed. Its disadvantages are a prolonged course, a retained tube or plug, patient compliance, and the need for repeated review - and it still requires histopathology of any tissue removed.

What I would tell the patient:

• This is an incidental finding. It is not cancer on the radiograph, but it is a cyst-like growth that will slowly enlarge and thin the jaw if left, and it needs to be removed.
• We cannot tell exactly what it is from the X-ray; the answer comes from the laboratory after removal.
• Most of these are harmless and are cured by removal, but a minority (keratocysts in particular) can come back, so follow-up radiographs are needed for several years.
• The specific risks: numbness of the lower lip on that side (temporary or, less commonly, permanent) because of the closeness to the nerve; swelling, bruising, infection, and, rarely, fracture of the jaw.
• He should stop smoking, both for healing and for general risk.
• Refer to oral and maxillofacial surgery, and record the discussion.

Interpretation: uniform opacification of one maxillary sinus on a panoramic radiograph is a non-specific finding. It usually represents mucosal thickening or fluid, and in this man the recent 'cold' a month ago makes inflammatory thickening the most likely explanation. Panoramic images are poor for sinus assessment - they show only part of the sinus, are distorted, and cannot distinguish mucosa from fluid, polyp or mass.

Differential: mucosal thickening from recent or chronic sinusitis; retention cyst or polyp; fluid; odontogenic sinusitis from an infected upper molar (check the periapical status of 16, 17, 18); and, least likely but most important not to miss, a neoplastic process.

Action:

1. Assess clinically: ask specifically about unilateral nasal obstruction, blood-stained discharge, epistaxis, facial pain or swelling, loosening of upper teeth, and paraesthesia of the upper lip or cheek - all red flags for malignancy. Examine the nose and oral cavity, and test the vitality of the upper right posterior teeth.
2. Do not treat empirically with antibiotics for a finding he has not complained of.
3. Review in 4-6 weeks if there are no red flags and the history fits recent infection; consider a repeat or dedicated sinus view. Many post-inflammatory thickenings resolve.
4. Refer to ENT if there are any red flags, if the opacity persists on review, if it is associated with a non-vital upper molar requiring dental treatment, or if symptoms develop. Persistent unilateral sinus opacity in a smoker over 50 warrants nasendoscopy.

What would change management: unilateral bloody discharge, a mass visible in the nasal cavity, paraesthesia, mobile upper teeth with vital pulps, or an expanding opacity - these convert a 'review' into an urgent referral. Documenting the discussion and the review plan is essential, because an unexplained unilateral sinus opacity is a recognised source of delayed diagnosis.