Abstract
Odontogenic keratocyst (OKC) rarely appears in the buccal space. It is aggressive and infiltrative, and simple enucleation results in high recurrence. This case report describes an OKC located in the buccal space recurring twice in a 62-year-old man with a 25 mm diameter cystic lesion in the right pterygomandibular space. The multicystic lesion was enucleated. Subsequently, a recurrence was observed, and the gourd-shaped recurrent lesion was also enucleated. The difficulty in detaching the mass from the scar tissue resulted in the perforation of the cystic wall. Thereafter, a second recurrence was observed, and the tissue surrounding the unicystic recurrent lesion was excised. The histopathological features were consistent with those of OKC. The present case is the 11th reported case of OKC in the buccal space and the first with apparent recurrence. Since complete enucleation in the pterygomandibular space is difficult, excision along with the surrounding tissues could prevent recurrence.
Keywords: dentistry and oral medicine, pathology, oral and maxillofacial surgery
Background
Odontogenic keratocysts (OKCs) are one of the most common odontogenic cysts of ectodermal origin.1 They occur both in the maxilla and the mandible; however, in most cases, the mandible has a predilection for the molar-ramus region.2–6
OKC is typically recognised as an odontogenic cyst occurring intraosseously, and the histogenesis of intraosseous OKC can be attributed to the sources of odontogenic epithelium, that is, the dental lamina and its remnants, and the extensions of the basal cells from the overlying epithelium.6–8 OKC occasionally arises from the gingiva as a peripheral manifestation1 6 9–11; however, extremely rare cases of parakeratinised cysts arising from the buccal space, apart from the jawbone, with histopathological features identical to OKC, have been reported.1 2 4–8 12
Despite its benign appearance, the characteristics of OKC are potentially aggressive, showing infiltrative growth, with solitary or multicystic formations of odontogenic origin, with high rates of recurrence of approximately 62.5%.4 8 13 Simple enucleation of intraosseous OKC has resulted in high recurrence rates; therefore, complete eradication of the cystic lesion is necessary to decrease or eliminate recurrences.4 14 If not removed appropriately, OKC can recur in approximately 62.5% of cases.8
In this report, we present a case of OKC arising from the buccal space and showing two recurrences. We also conducted a literature review on the characteristics and surgical procedures of OKC in the buccal space.
Case presentation
In 2017, a 62-year-old man was presented with a painful swelling in the right buccal mucosa, which had significantly increased in size over the last 1 week. Clinical examination revealed an elastic, firm, mobile nodule in the right buccal mucosa. The mass was located separately from the parotid papilla and the overlying mucosa was normal. Mouth opening was hindered to some extent.
Investigations
On MRI, the mass in the pterygomandibular space revealed multicystic hyperintensity with a maximum diameter of 25 mm on T2-weighted images (figure 1). Although the biopsy sample was obtained from the buccal mucosa intraorally, the histopathological findings revealed only granulation tissue. OKC was not included in the clinical differential diagnosis and the preoperative diagnosis could not be determined. Therefore, the cystic lesion was enucleated under general anaesthesia. Dissection through the buccal mucosa and buccinator muscle revealed a mass. Detachment of the mass from the surrounding tissue was difficult. The specimen was submitted for pathological examination (figure 2), which revealed a histomorphology consistent with an OKC. Approximately 2 years following the initial operation, a recurrence of the mass was observed. The clinical findings were similar to those noted previously (figure 3). MRI revealed a gourd-shaped hyperintensity with a maximum diameter of 20 mm on T2-weighted images (figure 4). A second enucleation was performed intraorally under general anaesthesia. Since detaching the mass from the surrounding scar tissue was extremely difficult, the cystic wall was perforated and gray-beige contents were observed (figure 5). Histopathological examination of the specimen covered by scar tissue resulted in the diagnosis of OKC (figure 6). Approximately 6 months following the second operation, recurrence was observed again, and MRI revealed a unicystic hyperintensity with a maximum diameter of 10 mm on the T2-weighted images (figure 7).
Figure 1.
Heterogeneous multicystic hyperintensity on T2-weighted images (yellow arrow).
Figure 2.
The mass detached from the surrounding tissues.
Figure 3.
An elastic firm mobile mass palpable under the right buccal mucosa.
Figure 4.
Homogeneous gourd-shaped hyperintensity on T2-weighted images (yellow arrow).
Figure 5.
Gray-beige contents drained from the perforated cyst.
Figure 6.
The mass surrounded by a scar tissue.
Figure 7.
Homogenous unicystic hyperintensity on T2-weighted images (yellow arrow).
Treatment
Excision, including the removal of the adjacent buccinator, masseter and medial pterygoid muscle, was performed intraorally under general anaesthesia. Although they appeared normal, the overlying mucosa and proximal bone were partially removed (figure 8). The specimen was a non-perforated cyst accompanying the oral mucosa, muscle and periosteum (figure 9).
Figure 8.
Intraoperative view after excision of the mass along with the adjacent muscle and proximal bone.
Figure 9.
The excised mass along with the oral mucosa, muscle and periosteum.
Histologically, H&E-stained sections revealed unilocular cysts with the conventional OKC lining (figure 10A). The lesion was lined by squamous epithelium with corrugated parakeratinisation on the surface and included keratin in the cystic cavity (figure 10B). Immunohistochemically, the lining epithelium was positive for CK17, while the basal and parabasal cells were positive for Ki-67 (Figure 10C, D). These features are consistent with those of OKC.
Figure 10.
Histological findings. (A) Cyst surrounded by fibrous connective tissue containing muscles and mucous salivary lobules (original magnification ×12.5). (B) The lining epithelium with a flat basal line and corrugated parakeratinisation on the surface includes keratin within the cystic cavity (original magnification ×200). (C) CK17 is positive in the entire epithelial layer of the cyst lining (original magnification ×200). (D) Ki-67 positive cells are located mainly in the parabasal layer (original magnification ×200).
Outcome and follow-up
No clinical evidence of recurrence was observed at 1 year following the third surgery.
Discussion
We identified two important clinical issues in this study. The odontogenic origin of OKC is controversial, and besides the jawbone or gingiva, it can occur in the buccal space also, although such cases are extremely rare. Furthermore, OKC of the buccal space can recur if enucleation rather than excision is performed due to the anatomical complexity of the buccal space with the adjacent jawbone and muscles that makes complete enucleation technically difficult.
The origin of OKC in the buccal space, rather than as intraosseous or peripheral lesions associated with the mandible or maxilla, is still controversial.1 4 7 8 12 The hypotheses for such an origin include: (1) the epithelial lining of the OKC in the buccal space may originate from the sebaceous duct epithelium due to a striking similarity in the lining between them.8 15 Sebaceous glands are commonly located in the buccal mucosa as Fordyce spots. (2) Keratocyst of epidermal origin may occur ectopically in the buccal mucosa, which is referred to as an epidermal inclusion cyst or a cutaneous keratocyst.8 12 (3) Dental lamina rests may be displaced and persist in the buccal mucosa during odontogenesis, which could be conceptualised as ‘odontogenic.’12
A review of the existing literature identified only 10 cases of OKC in the buccal space, excluding cases involving the temporalis muscles and soft palate/pharynx (table 1).1 2 4–8 12 16
Table 1.
Summary of the findings of OKC in the buccal space from the literature review
| Authors (year) | Age | Sex | Location | Size | Imaging modality |
| Precheur and Krolls (2009)2 | 59 | M | Right buccal space | 31×22 mm | CT |
| Ide et al (2010)12 | 60 | M | Left buccal mucosa | 30×20×20 mm | – |
| 16 | M | Right buccal mucosa | 5 mm | – | |
| Gröbe et al (2012)4 | 52 | M | Right buccal space | 20×20×10 mm | PR, CT |
| Yamamoto et al (2013)1 | 74 | M | Right buccal mucosa | 35 mm | CT, MRI |
| Kaminagakura et al (2013)7 | 37 | M | Left buccal mucosa | 20×15 mm | US |
| Zhu et al (2014)5 | 69 | M | Right buccal mucosa | 20 mm | PR, CT, MRI |
| Makarla et al (2015)6 | 62 | M | Right buccal space | 48×45 mm | CT |
| Witteveen et al (2018)8 | 63 | M | Right buccal space | 18 mm | PR, MRI |
| 48 | F | Left buccal space | – | PR | |
| Present case (2021) | 62 | M | Right buccal mucosa | 25 mm | PR, CT, MRI |
| Authors (year) | Biopsy | Preoperative diagnosis | Treatment | ||
| Precheur and Krolls (2009)2 | Aspirated and incisional | Ectopic OKC | Excision | ||
| Ide et al (2010)12 | – | – | Removal | ||
| – | – | – | |||
| Gröbe et al (2012)4 | – | – | Excision | ||
| Yamamoto et al (2013)1 | Aspirated | Epidermoid cyst | Extirpation | ||
| Kaminagakura et al (2013)7 | Aspirated | Epidermoid cyst | Excision | ||
| Zhu et al (2014)5 | – | – | Extensive resection | ||
| Makarla et al (2015)6 | – | Non-specific chronic abscess | Excision | ||
| Witteveen et al (2018)8 | – | – | Excision | ||
| Incisional | OKC | Excision | |||
| Present case (2021) | Aspirated and incisional | Granulation tissue | Enucleation, excision | ||
| Authors (year) | Staining method | Follow-up | |||
| Precheur and Krolls (2009)2 | HE | – | |||
| Ide et al (2010)12 | HE, CK10, CK16, CK17, CK19, Ki-67, D2-40, Bcl-2 | No recurrence | |||
| HE, CK10, CK16, CK17, CK19, Ki-67, D2-40, Bcl-2 | – | ||||
| Gröbe et al (2012)4 | HE | No recurrence after 4 months | |||
| Yamamoto et al (2013)1 | HE, CK10, CK17, Ki-67, | No recurrence after 4 years | |||
| Kaminagakura et al (2013)7 | HE, CK17, CK19, Bcl-2, mTOR, Shh, Smo, PTCH-1 | No recurrence after 1 year | |||
| Zhu et al (2014)5 | HE | – | |||
| Makarla et al (2015)6 | HE, Ki-67 | No recurrence after 2 years | |||
| Witteveen et al (2018)8 | HE | No recurrence after 4 years | |||
| HE | No recurrence after 1 year | ||||
| Present case (2021) | HE, CK17, Ki-67 | Two times recurrence after 4 years |
–, not stated; CT, computed tomography; F, female; HE, hematoxylin and eosin; M, male; MRI, magnetic resonance imaging; OKC, odontogenic keratocyst; PR, panoramic radiography; US, ultrasound.
Among these cases, most of the patients were men, and the age of onset ranged from teenage to the seventies. The location of the lesions was described as the ‘buccal space’ or ‘buccal mucosa’. The largest OKC of the buccal space had a maximum diameter of 48 mm, and panoramic radiography, CT and MRI were mainly used as imaging modalities. Radical approaches, such as excision, extirpationand extensive resection, were performed in eight cases. Of the four biopsies performed, two lesions were excised based on the preoperative diagnosis of OKC. H&E staining was performed in all cases, while immunohistochemical analysis with CK17 or Ki-67 was performed in half of them. No apparent recurrence was observed in any of the cases, with a maximum reported follow-up of 4 years.
There are various clinical differential diagnoses of the swelling of the buccal mucosa. The patients’ medical history can provide important clues regarding odontogenic inflammation, while histopathological findings from a diagnostic biopsy are mandatory for benign and malignant lesions.4 CT and MRI, especially the latter, of soft tissue OKC can provide important information, since plain radiography may not show apparent changes.5 Makarla et al6 described that intraosseous OKC generally proliferates within the marrow spaces and does not produce large cortical expansion, while OKC in the buccal soft tissues tends to expand uniformly on all sides, presenting a large buccal swelling as the main clinical presentation. In the present case, diagnosis could not be established by clinical examination, imaging and biopsy. Initially, total enucleation was performed since the MRI revealed a well-defined cystic mass despite its large expansion.
Typical histology of OKC shows an uninflamed fibrous wall lined by a folded, thin, regular parakeratininised epithelium of five to eight cell layers thick, without rete ridges, while epidermoid cyst histologically reveals a cystic cavity filled with large amounts of keratin flake lined by orthokeratinised stratified squamous epithelium with prominent stratum granulosum.6 17 These types of keratinised cysts show similar histopathological features; however, previous studies suggested that soft tissue OKC could be differentially diagnosed from epidermoid cysts by their immunohistochemical profiles for CK17 and Ki-67.1 16 18 The expression of CK17 in OKC was widely and strongly positive in all epithelia; however, in epidermoid cyst, it was weakly and locally positive in keratinised cells.18 On the other hand, Ki-67-labelled cells were higher in OKC, suggesting higher proliferation potential.1 18 Predominant suprabasal distribution of Ki-67-labelled cells is also a characteristic of OKC.1 Summarily, the localisation of Ki-67-positive nuclei is different between OKC and epidermoid cyst.18 Furthermore, histologically, dermoid cysts are surrounded by keratinising squamous cells and contain adnexal structures, such as hair follicles, sweat glands and sebaceous glands.19 A previous study reported that CK17 was expressed in OKC, but not in dermoid cyst, suggesting that the epithelial lining of OKC has neoplastic characteristics.20 In the present case, the immunohistochemical profiles of the lining epithelia were consistent with those of OKC. Then, histopathological findings showed no adnexal structures, although surrounding tissue around cyst wall contained muscles and mucous salivary lobule. Therefore, we eventually diagnosed the present case as OKC.
Intraosseous OKC is aggressive and infiltrative, demonstrating high recurrence rates. The recurrence rate of soft tissue OKC is reportedly 12.5%–13.6%.7 8 16 21 Emerson et al22 suggested that care should be taken to avoid the contamination of tissues by cystic epithelium during surgery, since recurrence may develop due to traumatic implantation of cystic tissue in the surrounding soft tissue.23 Giuliani et al14 described that excision of adjacent bone and soft tissue in continuity with the cystic lesion can be advisable when incomplete enucleation of the lesion due to adherence of the keratocyst’s thin lining to the adjacent structure occurs. Stoelinga et al24 stated that OKC elimination of the epithelial islands and microcysts located in the overlying, attached mucosa should be assured by surgically excising this part of the mucosa to prevent recurrence. In the present case, the first recurrence could possibly be due to the incomplete enucleation of the widespread extension of the multicystic mass into the pterygomandibular space. We performed the second enucleation because the recurrent lesion was relatively large and the excision with safety margins could result in postoperative functional impairment. The second recurrence could have been due to the contamination of tissues by the perforated cyst wall due to the difficulty of detachment from the surrounding scar tissue. In the third operation, a small unicystic mass was excised along with the overlying attached mucosa and the proximal bone, resulting in no recurrence to date.
The present case is the 11th reported case of OKC occurring in the buccal space and the first case with apparent recurrence among them. Since OKCs can occur in soft tissues also, besides intraosseous or peripheral areas, they should be included in the differential diagnosis of cystic lesions in the buccal space. For treating buccal space OKCs, excision with the surrounding tissue may effectively prevent recurrence, since complete enucleation in the pterygomandibular space, which has a complex structure bounded by the mandibular ramus, masseter, buccinator and medial pterygoid muscles, can be technically difficult. The main histopathological differential diagnoses for a soft tissue keratocyst include epidermoid cysts, cutaneous keratocysts, trichilemmal cysts and steatocystomas.6 7 Since many unanswered questions regarding the occurrence of keratocysts remain, further research is required to elucidate the histological characteristics, including the origin and nature of the disease.
Learning points.
Odontogenic keratocysts (OKCs) should be included in the differential diagnosis of cystic lesions in the buccal space.
The characteristics of OKC are potentially aggressive with high rates of recurrence.
For treating buccal space OKCs, excision with the mandibular ramus, masseter, buccinator and medial pterygoid muscles could effectively prevent recurrence.
Footnotes
Contributors: TW wrote up the case report and performed a literature review on odontogenic keratocyst in the buccal space.
Funding: The author has not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests: None declared.
Provenance and peer review: Not commissioned; externally peer reviewed.
Ethics statements
Patient consent for publication
Consent obtained directly from patient(s).
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