Abstract
Introduction
Keratocystic odontogenic tumors (KCOTs) are cystic tumours originating from the dental lamina of the maxilla and mandible that are lined with keratinized epithelium. While benign, they can be locally destructive and have a high recurrence rate despite treatment. Rarely, KCOTs may undergo malignant transformation into Primary Intraosseous Squamous Cell Carcinoma (PIOSCC).
Case report
This study reports the clinical findings, radiological scans and histopathology of 2 patients with KCOTs that underwent malignant transformation into PIOSCC.
Discussion
A comprehensive literature review was performed to similar reports documenting the malignant transformation of KCOTs. The potential for KCOTs to undergo malignant change should prompt oral maxillofacial surgeons and otolaryngologists to exercise a high index of suspicion when treating these lesions. Patients persisting with unresolved disease after treatment should be investigated for malignant transformation. Detailed histopathological examination of KCOT specimens is recommended to detect small foci of SCC which may be present in the epithelium.
1
Introduction
The keratocystic odontogenic tumour (KCOT), previously known as the odontogenic keratocyst (OKC) , was first described by Philipsen in 1956 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” . While not known to metastasize, these lesions are locally destructive and have a high recurrence rate of 25%–60% . Approximately one-third are asymptomatic and detected on routine dental examination, while 50% present with jaw swelling and 25% with mild pain. Molecular analysis studies have demonstrated KCOTs are neoplastic, with deletion of multiple tumour suppression genes .
It has been reported that KCOTs may undergo malignant transformation into squamous cell carcinoma (SCC) . Also known as primary intraosseous squamous cell carcinoma (PIOSCC), these lesions arise within the jawbones from odontogenic epithelium and have no initial connection with oral mucosa . Recent reviews place the total number of reported cases at around 16 , with a mean age of 60.2 years and a male:female ratio of 2.2:1. While odontogenic cysts are relatively common, malignant transformation is a rare occurrence with rates estimated to range from 0.1% to 1.8% .
The clinical and radiologic features of PIOSCC are similar to benign odontogenic tumors and cysts. Swelling and pain were the most common complaints, with the mandible (79%) being more commonly involved than the maxilla (21%) . Other late features include chronic infection, perforation of the buccal, lingual or palatal cortical plates, adherence of the cyst lining to the bony cavity and chronic sinus tract.
PIOSCC behaves in a similar fashion to oral SCC. The majority (85%) of PIOSCCs are well or moderately differentiated SCC. The overall survival rate of individuals with PIOSCC was 62% at 2 years and 38% at 5 years. The treatment approach for PIOSCC is similar to that of oral cancer, with en bloc resection of the lesion with reconstruction and neck dissection (if indicated), followed by postoperative chemoradiation .
We report 2 cases of KCOTs that underwent malignant transformation into PIOSCC and review the literature relevant to this uncommon entity.
2
Case report
2.1
Case 1
Our first patient is a 45 year old Chinese man who has a history of ischemic heart disease with coronary stenting in 2007. He is an ex-smoker who smoked a pack of cigarettes a day for 20 years, but quit in 1998.
In 2004, he presented to the Ear, Nose and Throat Department of Singapore General Hospital (SGH-ENT) with painless swelling of the left nasolabial region for a year. Examination revealed a mass on the left maxilla which appeared cystic on the orthopantomogram (OPG). Initially diagnosed to have a globulomaxillary cyst, he was referred to the oral maxillofacial surgeons for excision. The cyst was excised via Caldwell Luc approach in May 2004, with histopathological examination of the specimen revealing a KCOT.
He returned to the department in 2006, complaining of tightness in the left maxillary area. On examination, there was mild swelling of his left maxilla. Computed tomography (CT) scans of his paranasal sinuses showed a rim enhancing cystic lesion in his left maxillary sinus measuring 3.4 cm in diameter ( Fig. 1 A ). The medial, lateral and anterior walls of the left maxillary sinus were breached and the left infraorbital canal was dehiscent. His case was discussed between the attending physicians and a decision was made for radial resection of the tumor. In July 2006, he underwent left total maxillectomy with removable palatal obturator and split skin graft. Histology of the resected specimen showed a cyst with keratinizing stratified squamous epithelium, in keeping with a keratocystic odontogenic tumour (KCOT) ( Fig. 1 B). No evidence of malignancy was seen. Postoperatively, he recovered swiftly and was discharged from the hospital.
His follow up visits were uneventful no disease was detected for over 2 years, until he returned in February 2009 complaining of left eye redness and swelling which were associated with fever and chills. Magnetic Resonance Imaging (MRI) scan of the orbits showed left orbital inflammation with proptosis. Patient was treated as for orbital cellulitis and given IV antibiotics. The patient responded to antibiotic treatment and did not experience any visual loss. Follow up MRI scans showed a soft tissue mass at the inferolateral aspect of the left orbit compatible with local tumour recurrence. Endoscopic biopsy of lesion showed recurrent KCOT. The recurrent tumour tissue was excised endoscopically from left floor of orbit.
Despite frequent follow ups and repeated nasal toilets, the KCOT continued to be symptomatic and a discharging cutaneous fistula at the lateral aspect of the left eye developed.
In March 2011, he once again reported swelling of his left cheek and examination revealed swelling around the left zygoma. A CT scan of the sinuses showed recurrent tumour in the infraorbital region, extending superiorly into the orbit, medially into the posterior ethmoidal air cells, laterally to involve the zygoma and posteriorly into the pterygopalatine fossa and pterygoid maxillary fissure ( Fig. 1 C). The bone surrounding the lesion appeared sclerosed and fragmented. As the patient was not keen for another surgery, the attending surgeon continued to treat the patient conservatively.
The patient’s symptoms did not improve and the constant facial tightness and discharge from the fistula were a source of distress. Eventually, the patient opted for further surgery. In May 2012, he underwent a left extended maxillectomy to resect the recurrent KCOT. The surgery went well and the patient recovered quickly. However, histopathological examination of the specimen revealed a focus of well differentiated squamous cell carcinoma at the infraorbital margin ( Fig. 1 D). His case was presented at the institutional tumour board meeting and a multidisciplinary decision was made for him to receive complete surgical excision of the cancer with post op radiotherapy.
In June 2012, he received a left extended maxillectomy with orbital exenteration and split skin graft in May 2012. The surgery was complicated by cerebrospinal fluid (CSF) leak, and the defect was closed with abdominal fat and septal cartilage and sealed with tissue glue. Resection margins were all clear. Paraffin sections found 2 separate foci of well differentiated squamous cell carcinoma, Grade 1 T3N0M0, 2.5 cm and 2 cm respectively. The patient recovered from surgery well and did not develop any neurological complications.
He completed postoperative radiotherapy (26 grays in 13 fractions) and is currently well, with no evidence of disease recurrence.
2.2
Case 2
Our 2nd patient is a 49 year old Chinese man with no significant past medical history.
In December 2006, he had his left lower third molar extracted due to impaction. Post-extraction, he experienced swelling of his left mandible for 4 months, which resolved with oral antibiotics given by his private dentist. In November 2007, he had his first and second left lower molars extracted by his private dentist due to gum disease. Post-extraction, he developed fever, jaw pain, jaw swelling, trismus and oral discharge.
He presented a month later in December 2007 to the National Dental Centre of Singapore (NDCS) with the above symptoms. Examination revealed multiple discharging intraoral sinuses along his left mandible, while OPG revealed irregular areas of radiolucency along the left mandible in the molar region ( Fig. 2 A ). CT scan findings supported the clinical diagnosis of osteomyelitis of the mandible and a wound debridement with sequestrectomy was performed. Histological examination of tissue specimens showed chronic inflammation with bony sequestrum. Tissue cultures demonstrated a mixed growth of aerobes and anaerobes. An Infectious Diseases physician was consulted and the patient started on oral amoxicillin with clavulanic acid.
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