A multilocular radiolucency in the posterior mandible

Differential diagnosis of a multilocular radiolucency in the posterior mandible of a young adult:

• Odontogenic keratocyst (OKC): often multilocular, grows along the bone, may cause minimal expansion; aspirate is typically keratinous/cheesy, not straw-coloured.
• Ameloblastoma: classic soap-bubble multilocular radiolucency, often causes expansion and root resorption; aspirate may be straw-coloured.
• Odontogenic myxoma: multilocular, often with fine trabeculae ("tennis racket"), may cause expansion.
• Dentigerous cyst: associated with an unerupted tooth; usually unilocular.
• Central giant cell granuloma: multilocular, often anterior mandible, younger patients.
• Aneurysmal bone cyst: rare, often expansile.
• Metastatic or other malignancy: less likely in this age group but must be considered.

Narrowing:

• Aspirate: straw-coloured fluid is more consistent with a cyst or ameloblastoma than with OKC (keratin) or a solid tumour; send for cytology and protein content.
• Imaging: CT or CBCT to assess cortical expansion, perforation and internal structure; MRI if soft tissue extent is unclear.
• Vitality testing of adjacent teeth confirms the lesion is not inflammatory.
• Incisional biopsy is the definitive step before definitive surgery, especially if the lesion is large or if malignancy is a consideration.

The key is not to commit to enucleation before histology, because management differs substantially between OKC, ameloblastoma and myxoma.

Management options for OKC:

• Enucleation with adjunctive measures: curettage of the bony walls, peripheral ostectomy, or application of Carnoy's solution (where available) to reduce recurrence.
• Marsupialisation followed by enucleation: useful for large lesions to shrink the cyst and preserve bone; may be used as a two-stage approach.
• Resection (marginal or segmental): reserved for recurrent or aggressive lesions with cortical perforation.
• Regular radiographic follow-up is essential.

Counselling about recurrence:

• OKC has a high recurrence rate (often quoted around 10–30% depending on treatment and follow-up), related to satellite cysts, incomplete removal and the thin friable lining.
• Recurrence can occur many years later, so long-term follow-up (e.g., annually for at least 5 years, often longer) is needed.
• The patient should be told about the possibility of further surgery, the need for imaging, and the importance of reporting swelling, pain or paraesthesia.
• If the patient has multiple OKCs, consider nevoid basal cell carcinoma syndrome (Gorlin syndrome) and refer for assessment (skin, skeletal, family history).

The key judgement is balancing the desire for cure against morbidity, and committing to long-term surveillance.

Features suggesting Gorlin syndrome:

• Multiple OKCs, especially at a young age or in multiple quadrants.
• Multiple basal cell carcinomas, especially on sun-exposed skin, or palmar/plantar pits.
• Skeletal anomalies: bifid ribs, frontal bossing, calcification of the falx cerebri.
• Family history of similar features.
• Medulloblastoma in childhood.

If suspected:

• Take a detailed family history and examine the skin for basal cell carcinomas and palmar pits.
• Refer to a clinical geneticist for assessment and possible genetic testing (PTCH1/SMO pathway).
• Arrange appropriate imaging (e.g., skull radiograph or CT for falx calcification, chest radiograph for rib anomalies).
• Counsel the patient about sun protection and skin surveillance, and involve dermatology.
• Inform the patient that offspring have a substantial risk and that genetic counselling is available.

Recognising the syndrome changes management from a single cyst to a lifelong multidisciplinary surveillance plan.