An Orthokeratinized Odontogenic Cyst in an 8-Year-Old: A Case Report with Differential Diagnosis

ABSTRACT

Background

Orthokeratinized odontogenic cyst (OOC) is a rare developmental odontogenic cyst that is clinically and histomorphologically different than odontogenic keratocyst (OKC).

Case Description

OOC is a distinct entity from OKC with a unique biological behavior, pathogenesis, and prognosis. The distinction between these entities is paramount because unlike OKCs, OOCs rarely recur after simple enucleation and are not associated with nevoid basal cell carcinoma syndrome. We present a case of an 8-year-old male with an OOC of the right posterior mandible along with a differential diagnosis and discussion of OOCs and its common mimics.

KEYWORDS:

• Clinicopathologic conference
• differential diagnosis
• mandibular cyst
• odontogenic cyst
• orthokeratinized odontogenic cyst
• unilocular lesion
• pediatric jaw cyst

Introduction

An orthokeratinized odontogenic cyst (OOC) is a developmental odontogenic cyst that is predominantly or entirely lined by orthokeratinized squamous cell epithelium.^1,2 OOCs are rare; they represent less than 1% of odontogenic cysts and approximately 10% of all keratinizing odontogenic jaw cysts.³ OOCs are a distinct entity from the odontogenic keratocyst (OKC).^1,2 Unlike OKCs, OOCs respond extremely well to simple enucleation and have a recurrence rate of <2%.⁴ OOCs also lack PTCH1 gene mutations,⁵ are not associated with nevoid basal cell carcinoma syndrome,⁶ and exhibit different histopathological features than OKCs.^1,2

OOCs occur over a wide age range but are most common during the third and fourth decades of life.^1,5 OOCs are more common in males.^1,3,7 Approximately 75% to 90% of cases involve the posterior mandible.^3,8

OOCs often present as painless swellings, but they may be asymptomatic and incidentally detected on radiographs.^3,5,7 On radiographs, the vast majority of OOCs present as well-demarcated unilocular radiolucent lesions.^1,5 Approximately 9% of cases are multilocular.⁵ OOCs are often associated with unerupted teeth and may mimic dentigerous cysts on radiographs.^4,7 Multifocal OOCs are rare but have been reported.⁶

We present a case of an OOC of the right posterior mandible in an 8-year-old male. This case report presents a differential diagnosis of this mandibular lesion and discusses clinical, radiographic, and histological mimics. Frequently, these cysts are incidentally detected on routine radiographs by the dental team. The diagnosis and management of these lesions frequently requires the collaboration of dental and medical specialists including pathologists, surgeons, radiologists, and general practitioners.

Clinical Presentation

A pediatric dentist referred an 8-year-old male to an oral and maxillofacial surgeon for further evaluation and management of an expansile radiolucent lesion of the right posterior mandible that was detected on a panoramic radiograph (Figure 1). The parents stated that the child’s previous dental appointment was two years prior in a foreign country. The parents did not recall any imaging being obtained or discussing a mandibular lesion at the prior appointment. The parents first noted enlargement of the right posterior mandibular alveolar ridge six months prior to presentation with the oral and maxillofacial surgeon. The patient and his parents reported slow intermittent swelling in the area and denied any history of localized pain, infection, or trauma.

Figure 1. Panoramic radiograph demonstrating an expansile, well-circumscribed, unilocular radiolucency of the right posterior body and angle regions of the mandible causing displacement of the second premolar and second molar.

The child’s past medical history was noncontributory. He was not taking any medications and his parents reported no known drug or seasonal allergies. The parents reported only that the child experienced very mild discomfort upon palpation, but they were concerned with the recent enlargement.

A systemic examination was unremarkable, showing no signs of distress or abnormal vital signs. Only a very mild lower facial asymmetry extraoral was noted with his right mandibular angle area slightly more pronounced than the left. Intraorally, the right posterior mandibular body and ramus areas were mildly enlarged compared to the contralateral side. Compression of the nonerythematous enlarged areas did not result in pain or exudation. No sinus tracts or fistulas were noted in the area. The right mandibular second premolar (tooth No. 29) was malpositioned distoangularly, while the partially erupted first molar (tooth No. 30) demonstrated significant mobility. The overlying alveolar mucosa was intact with no noted perforations or mucosal openings. All teeth in the quadrant were normal in color, but vitality testing was inconclusive given the patient’s behavioral ability to tolerate testing.

A medical computed tomographic (CT) scan was obtained (Figures 2–4), which revealed an expansile osteolytic lesion of the right mandibular body. The lesion appeared to be associated with or directly alongside the posterior right mandibular molar teeth. There was cortical thinning of the bone in the affected areas. Along the superior aspect at the midportion of the lesion appeared to be cortical discontinuity. The lesion measured approximately 2.9 cm × 2.1 cm in the coronal plane, while anterior to posterior measured up to 4 cm.

Figure 2. Axial CT image demonstrating the anterior-posterior dimension (approximately 4 cm) of an expansile, unilocular radiolucent lesion of the right posterior mandible. Note the significant asymmetry in buccal-lingual width compared to the contralateral side.

Figure 3. Coronal CT image demonstrating the vertical size (approximately 3 cm) of the expansile, unilocular radiolucent lesion of the right posterior mandible. The image also shows the posteriorly displaced crown of the second molar.

Figure 4. Sagittal CT image demonstrating the thinning of the superior and inferior cortices in the right posterior mandible. Also seen is the displaced crown of the second molar at the posterior-superior aspect of the lesion.

Differential Diagnosis

The differential diagnosis of an expansile and nondestructive radiolucent lesion of the posterior mandible in an 8-year-old male is broad. Although the clinical and radiographic features of this case were nonspecific, common odontogenic cysts such as dentigerous and radicular were quickly eliminated. A dentigerous cyst was not considered because the lesion did not envelop the crown of an unerupted tooth. Instead, the lesion displaced the right second premolar and mandibular molars. A radicular cyst was not considered, as an odontogenic infection seemed improbable because the patient lacked gross carious lesions or a confirmed non-vital tooth in the right posterior mandible. The radiolucent lesion’s large size, involvement of the right mandibular body and ramus, and nondestructive behavior were most suggestive of a cyst or benign tumor of the jaws. OKCs, ameloblastic fibroma, and central giant cell granuloma were the top three considerations in the differential diagnosis.

An OKC is a developmental odontogenic cyst characterized by a thin lining of parakeratinized stratified squamous epithelium with hyperchromatic palisading basal cells.² OKCs are common and represent 4–12% of all odontogenic cysts.⁹ Most OKCs present as asymptomatic radiolucencies and are incidentally found on radiographs. The most common locations are the posterior body (90% occur posterior to the canines) and the ramus of the mandible (more than 50%).¹⁰ Lesions tend to grow along the internal aspect of the jaws, but slight expansion of the cortical plates is not uncommon.

The ameloblastic fibroma (AF) is a benign, true mixed tumor of odontogenic mesenchyme and epithelial tissue resembling odontogenic mesenchyme with no dental hard tissues present.² AFs are most commonly found in children and adolescents (mean age 14.9 years)¹¹ and are usually painless and slow-growing tumors. The majority (56%) of AFs are small, unilocular radiolucencies that may represent developing odontomas. However, larger lesions and lesions in patients >22 years are more suggestive of a true neoplasm.¹¹

The central giant cell granuloma (CGCG) is a localized benign lesion of the jaws characterized by osteoclast-giant cells in a vascular stroma.² CGCGs occur across a wide range, but most cases are observed before age 20 years.¹² The most common presenting sign of a CGCG is a painless swelling.¹⁰ Radiographically, CGCGs generally appear similar to other benign odontogenic neoplasms and cysts. CGCGs typically present as slow growing, expansile, well-demarcated radiolucent lesions. However, larger, more aggressive lesions can become painful, exhibit tooth resorption, displace teeth, and perforate the cortical plates.¹³

Diagnosis and Management

After informed consent was obtained, the patient was taken to the operating room for treatment under general anesthesia. Using electrocautery, a crestal incision was made from the distal of the right mandibular canine extending posteriorly to the ascending ramus where a posterolateral releasing incision was made. A full thickness flap was then elevated to expose the body of the mandible, and a superior alveolar corticotomy (bone window) was created to access and visualize the lesion. An aspiration of the lesion captured minimal serous fluid with debris and caused no significant bleeding. An excisional biopsy and enucleation of the cystic-appearing lesion was performed in its entirety.

Though noted to be quite mobile, teeth No.29 and No. 30 were left in place with the expectation they might regain bone support as healing progressed. Hemostasis was obtained with pinpoint electrocautery, and an absorbable microfibrillar collagen hemostatic agent was placed into the defect to accelerate blood clot formation. The incision was then primarily closed with resorbable sutures. The specimen was submitted to medical pathology for histopathologic analysis.

Gross examination of the specimen revealed a gray and brown cystic lesion measuring approximately 4 cm in length and nearly 3 cm in height. Sections of the cystic lesion revealed a thin surface covering with a lumen containing a whitish cheesy-like material.

Hematoxylin and eosin sections revealed a thin, regular epithelium with a thick and lamellar orthokeratin layer lining a noninflamed fibrous wall (Figure 5a). The epithelial lining showed a prominent granular layer, and the cuboidal basal layer lacked hyperchromatic and palisaded nuclei (Figure 5b).

Figure 5. Histopathologic features of an OOC. (a) a thin, regular epithelium with a thick and lamellar orthokeratin layer lines a noninflamed fibrous wall (H&E stain, original magnification x 20); (b) the epithelial lining shows a prominent granular layer; the basal layer lacks hyperchromatic and palisaded nuclei (H&E stain, original magnification x 200).

The histologic features were consistent with OOC. Following complete excision of the lesion, the patient healed uneventfully and has remained disease free for over two years. Recurrence is unlikely, but the patient will be followed yearly both clinically and radiographically.

Discussion

OOCs are a rare developmental odontogenic cyst with defined histopathologic features and a less aggressive clinical behavior than OKCs. The pathogenesis of OOCs is still uncertain, with hypothesized origins including cell rests of dental lamina, oral epithelium influenced by dental papilla, and reduced enamel epithelium.^14,15 OOCs comprise 1% of all odontogenic cysts and 7–17% of all keratinizing jaw cysts.³

OOCs are rarely diagnosed in the first decade of life¹ and are more commonly seen in the third and fourth decades, affecting males more often than females (2–2.5:1).¹⁶ The true prevalence of OOCs in this population is difficult to assess due to a scarcity of reported cases. OKCs are more common than OOCs in pediatric populations and may be associated with nevoid basal cell carcinoma syndrome. OOCs are encountered twice as often in the mandible compared to the maxilla and are usually seen in the molar and ramus regions.⁸

Most OOCs are asymptomatic and are identified incidentally during radiographic investigation for other dental problems. Infrequently, patients with OOCs may demonstrate swelling with or without pain or dental mobility.¹⁷ Rarely, OOCs reach large enough size (greater than 7 cm) to cause cortical expansion, malocclusion, facial asymmetry, or paresthesia.¹⁸

Radiographically, most OOCs appear as a well-circumscribed unilocular radiolucency that may be associated with an unerupted tooth.¹⁹ Occasionally, the radiographic appearance of OOCs mimics a radicular cyst.

Histologically, the epithelial lining of an OOC is characterized by lamellar orthokeratin, a prominent granular cell layer, and a basal layer that is not hyperchromatic and not palisaded. Although it is generally agreed that an OKC also arises from the cell rests of the dental lamina,²⁰ OKCs are developmental odontogenic cysts lined with a thin corrugated layer of parakeratin. In OKCs, the basal epithelial layer is composed of hyperchromatic, palisaded cuboidal or columnar epithelium. Cords, islands of epithelium, and satellite cysts may also be observed within the fibrous walls of OKCs.²¹ OKCs and OOCs may contain a clear serum-like liquid or keratinaceous debris.²²

In general, OOCs tend to be smaller than OKCs and lack a comparable growth potential.^3,18 Most OOCs also demonstrate a less aggressive clinical behavior compared to OKCs,²³ which are more likely to occur at multiple sites and appear multilocular. OKCs may or may not be associated with impacted teeth. OOCs are generally solitary, asymptomatic, unilocular, and often associated with impacted teeth. OKCs can be associated with nevoid basal cell carcinoma syndrome²⁴ (Gorlin-Goltz syndrome), while OOCs are not associated with any syndromes.

Treatment of OOCs is by enucleation or careful surgical excision,^3,7 while the treatment for OKCs is somewhat more controversial and may include decompression, enucleation, and curettage followed by application of Carnoy’s solution or topical 5-fluorouracil (5-FU), or surgical resection.^25,26 Recurrence is rare for OOCs (<2%)²⁶ after simple nucleation but common for OKCs (12–58%).^27–29

Conclusion

Many cases of OOCs and OKCs are asymptomatic and discovered incidentally by general and/or pediatric dental and medical teams. Regular oral examinations and careful assessment of all routine imaging studies, especially panoramic radiographs in children, are critical to diagnose intraosseous lesions in a timely manner. OOCs are a distinct entity from OKCs. Unlike OKCs, OOCs are not associated with nevoid basal cell carcinoma syndrome and have an extremely low recurrence rate after enucleation. OOCs should be considered in the differential diagnosis of unilocular radiolucencies of the jaws.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Chan M. Park

Chan M. Park, DDS, MD is a staff oral and maxillofacial surgeon in the Department of Maxillofacial Surgery at Kaiser Permanente in Anaheim, California. He is a fellow in the American College of Surgeons and American College of Dentists. Conflict of Interest Disclosure: None reported.

Jeffrey A. Elo

Jeffrey A. Elo, DDS, MS is the Drs. Daljit & Elaine Sarkaria Professor of Advanced Oral Diagnosis & Therapeutics and a professor of oral and maxillofacial surgery at the Western University of Health Sciences College of Dental Medicine in Pomona, California; and is a clinical assistant professor in the department of oral and maxillofacial surgery at the Loma Linda University School of Dentistry in Loma Linda, California. He is a fellow in the American College of Surgeons, American College of Dentists, and International College of Dentists. Conflict of Interest Disclosure: None reported.

Mark Mintline

Mark Mintline, DDS is an associate professor of oral and maxillofacial pathology at the Western University of Health Sciences College of Dental Medicine in Pomona, California; and is the laboratory director of the WesternU Health Oral Pathology Laboratory.

Elizabeth Orbeta

Elizabeth Orbeta, MS is a dental student at the Western University of Health Sciences College of Dental Medicine in Pomona, California.

Stephen Seongeun Koh

Stephen Seongeun Koh, MD is a clinical pathologist at Kaiser Permanente in Anaheim, California. Conflict of Interest Disclosure: None reported.