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Site: posterior mandible – 18 anterior mandible -- 3 posterior maxilla – 6


Academic year: 2022

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原文題目(出處): Keratocystic odontogenic tumour: Reclassification of the odontogenic keratocyst from cyst to tumour. JCDA 2008;73:165-165h

原文作者姓名: Jonathan Madras, Henry Lapointe

通訊作者學校: Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario

報告者姓名(組別): 鍾芝華(Int. K 組) 報告日期: 97/04/15




to review the features and behaviour of the OKC (or KCOT);

to analyze a series of histologically confirmed KCOT cases;

to review and discuss the redesignation of KCOT and the implications for treatment In a case series of 21 patients (27 KCOTs), recurrence rate was 29%, all

recurrences occurred within 2 years after intervention.

WHO’s reclassification of this lesion from cyst to tumour : underscores its aggressive nature

motivate clinicians to manage the disease in a correspondingly aggressive manner

Most effective treatments are enucleation supplemented with Carnoy’s solution, or marsupialization with later cystectomy


Odontogenic keratocyst (OKC) is now designated by the WHO as a keratocystic odontogenic tumour (KCOT) and is defined as “a benign uni- or multicystic, intraosseous tumour of odontogenic origin, with a characteristic lining of parakeratinized stratified squamous epithelium and potential for aggressive, infiltrative behaviour.”

Case Series

21 patient files on 27 histologically confirmed KCOTs were reviewed

11 recurrences of lesions (5 elsewhere, 6 in author’s clinic) and 16 de novo lesions

Site: posterior mandible – 18 anterior mandible -- 3

posterior maxilla – 6


Treatment: enucleation and curettage -- 22

resection -- 2

marsupialization -- 3

Sample Cases

Patient 1 (born 1949, date of surgery: Dec. 16, 1999)

Recurrence of a KCOT (treated elsewhere 10 years earlier), multilocularity and extent of soft tissue involvement

Site: right mandible

Size: 45 cm2 radiographically

Follow up periods: 2 months to 7 years

Overall recurrence rate: 29%

All recurrences of lesions treated at author’s clinic were within 2 years

Average surface area of the lesions (radiographically) : 14 cm


Most lesions in 0–15 cm


range ( greatest number and proportion of recurrences)

No relation was found between age and

number of primary lesions among patient



Treatment: resection (complete removal of the right mandible from the condyle to the bone distal to tooth 44 )

Follow up 6 years: no recurrence

Patient 2 (born 1925, date of surgery: Nov. 22, 2001) primary KCOT

Site: left mandibular ramus Size: 19 cm2 radiographically Treatment: marsupializion Follow up 3.5 years: no recurrence

Patient 3 (born 1949, date of surgery: Sept. 17, 1993) de novo KCOT

Site: 18 cm2 radiographically Size: anterior mandible Treatment: curettage

Follow up 9 months: recurrence, this was curetted and followed up for 7 years


Clinical Features

11% of all cysts of the jaws

Occur most commonly in the mandible, especially in the posterior body and ramus regions Always occur within bone

Patients may present with swelling, pain and discharge or may be asymptomatic.

Local destruction and a tendency for multiplicity ( NBCCS or Gorlin-Goltz syndrome) High recurrence rate, reportedly between 25% and 60% (NBCCS—82%)

NBCCS : multiple KCOTs, nevoid basal cell carcinomas, bifid ribs, calcification of the falx cerebri, frontal bossing, multiple epidermoid cysts and medulloblastoma

3 mechanisms for KCOT recurrence (Brannon, 1976):

incomplete removal of the cyst lining,

growth of a new KCOT from satellite cysts (or odontogenic rests left behind after surgery) development of a new KCOT in an adjacent area

Recurrence rates: follow-up times, surgical technique used, no. of cases Mostly recurred within 5–7 years → long-term follow-up

Common Treatment Modalities

Morgan and colleagues : conservative or aggressive

Conservative treatment :“cyst-oriented”-- enucleation, with or without curettage, or marsupialization

Advantage: preservation of anatomical structures (including teeth)

Aggressive treatment: “neoplastic nature”-- peripheral ostectomy, chemical curettage with Carnoy’s solution or en bloc resection

Recommended for NBCCS cases, large KCOTs and recurrent lesions Site- and size-based approach to KCOT treatment planning

Removal of the mucosa overlying the lesion has been recommended : clusters of epithelial islands and microcysts with the potential to cause recurrence


Aggressive treatment → relatively low recurrence rates Conservative treatment → more recurrences

The most effective treatment option: enucleation of the KCOT and subsequent application of Carnoy’s solution

Alternatively, marsupialization followed by cystectomy is likewise effective KCOT: The Neoplasm

Factors that influenced WHO to reclassify KCOT:

Behaviour: KCOT is locally destructive and highly recurrent


Histopathology: basal layer of the KCOT budding into connective tissue, and mitotic figures are frequently found in the suprabasal layers

Genetics: PTCH (a tumour suppressor gene, occurs on chromosome 9q22.3-q31) PTCH binding to SMO(oncogene) inhibits growth-signal transduction. SHH binding to PTCH releases this inhibition.

The pathogenesis of NBCCS and sporadic KCOTs involves a “2-hit mechanism”, with allelic loss at 9q22.

1st hit: mutation in one allele, although it can be dominantly inherited, has no phenotypic effect

2nd hit: “loss of heterozygosity” (LOH). In KCOTs, leads to the dysregulation of the oncoproteins cyclin D1 and p53.

Implications and the Future of KCOT Treatment

The most appropriate action would be enucleation of the KCOT plus use of Carnoy’s solution or marsupialization followed by enucleation

Lesion size and associated recurrence are inconclusive (Forssell and others found that lesion size does not affect recurrence rate)

Taipale and colleagues,cyclopamine, a plant-based steroidal alkaloid, inhibits the cellular response to the SHH signal

Zhang and others postulate that antagonists of SHH signalling factors could effectively treat KCOTs ( intracystic injection of an SMO protein-antagonist)



The aggressive nature of KCOT warrants an aggressive treatment strategy

As researches continue, treatment may become molecular in nature→reduce or eliminate the need for aggressive methods

題號 題目

1 Which of the following statements is wrong?

(A) OKC may have scalloped outline radiographically

(B) The most common location of an OKC is the posterior body of the mandible (C) OKC showed cortical border radiographically

(D) The presence of internal keratin increase the radiopacity

答案(D) 出處:Oral Radiology-Principles and Interpretation (5th edition, pg 394) 題號 題目

2 Which of the following statements about NBCCS is wrong?

(A) Prevalence of Gorlin syndrome is estimated to be 1 in 50,000 (B) It is caused by mutations in PTCH, a tumor suppressor gene (C) Multiple basal carcinoma

(D) Odontogenic keratocyst

答案(A) 出處:Oral & Maxillofacial Pathology (2nd edition, pg 598)



Figure 10 Orthopantomogram (7 years after decompression and 2 years following enucleation) revealing the recurrence lesion, distending the mandibular body area spanned from right

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