Keratocystic odontogenic tumours (KCOT or KOT), previously known as odontogenic keratocysts, are benign cystic neoplasms involving the mandible or maxilla and are believed to arise from dental lamina. They are locally aggressive and tend to recur after excision.
On imaging, they typically appear as an expansile solitary unilocular lesion extending longitudinally in the posterior portions of the mandible. Although the majority are solitary, in 5-10% of cases multiple KOTs will be present: an associated condition such as basal cell naevus syndrome should be considered in these cases.
Present in younger patients (2nd-3rd decades) 1,7 and may be seen in either the body or ramus of the mandible (~70% of all keratocystic odontic tumours), or maxilla. There may be male predilection.
Commonly discovered incidentally. When symptomatic, jaw swelling and pain are a common clinical presentation of those tumours 8.
They originate from epithelial cell rests (stratified squamous keratinizing epithelium) found along the dental lamina and periodontal margin of the alveolus of the mandible 7.
basal cell naevus syndrome (a.k.a. Gorlin-Goltz syndrome)
- strong association
- consider the diagnosis if multiple KOTs are present
- Marfan syndrome
- Noonan syndrome
Panoramic radiograph / OPG
Typically seen as a solitary, lucent, unilocular lesion with smooth, corticated borders 5. When in the mandible, they typically grow along the length of the bone in anteroposterior dimension. In the maxilla, they expand into the maxillary sinus.
They can be associated with a crown of an unerupted/impacted tooth, mimicking a dentigerous cyst. Keratocystic odontogenic tumours can result in splaying and sometimes erosion of the adjacent tooth roots. They may occasionally appear septated, making the distinction from ameloblastoma difficult.
Keratocystic odontogenic tumours will typically demonstrate 3:
- T1: high signal due to cholesterol and keratin contents
- T2: heterogeneous signal
- DWI: restricts due to presence of keratin
- T1 C+: peripheral enhancement but unlike ameloblastomas no enhancing nodular component
Treatment and prognosis
They are locally aggressive. Treatment is often with enucleation/excision +/-aggressive curettage. However, they can have a very high recurrence rate (30-60%)
Imaging differential considerations include:
- dentigerous cyst if pericoronal
- calcifying odontogenic cyst (Gorlin cyst) and other odontogenic cysts and tumours
- 1. Dunfee BL, Sakai O, Pistey R et-al. Radiologic and pathologic characteristics of benign and malignant lesions of the mandible. Radiographics. 26 (6): 1751-68. doi:10.1148/rg.266055189 - Pubmed citation
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- 8. Grasmuck EA, Nelson BL. Keratocystic odontogenic tumor. Head Neck Pathol. 2010;4 (1): 94-6. doi:10.1007/s12105-009-0146-x - Free text at pubmed - Pubmed citation
- 9. Plunk M, Oda D, Parnell S et-al. American Journal of Roentgenology. 2016; . doi:10.2214/AJR.16.16587
Lucent lesions of the jaw