Glandular Odontogenic Cyst in Dentigerous Relationship: An Uncommon Case Report

Glandular odontogenic cyst (GOC) is an uncommon cyst of the jaw. Less than 200 cases are reported in the literature, and only 22 cases are associated with an unerupted tooth (dentigerous relationship). Although it is an asymptomatic lesion, it can be destructive and has high recurrence rates. The diagnosis can be especially challenging due to the lack of distinct diagnostic clinic-radiological criteria and nonspecific microscopic features, mimicking benign and malignant lesions. Conservative surgical treatment has been the choice for most surgeons, but marginal or partial jaw resection has been reported. This report describes a rare case of GOC in a dentigerous relationship, which was treated with enucleation and peripheral osteotomy.


Introduction
Glandular odontogenic cysts (GOCs) are uncommon jawbone cysts of odontogenic origin which were firstly described in 1987 by Padayachee and Van Wyk [1] as a "botryoid" odontogenic cyst with glandular component and denominated "sialo-odontogenic cyst." Gardner et al. [2] in 1988 established this cyst as a distinct entity-denominated glandular odontogenic cyst, which was classified as an odontogenic cyst by the WHO in 1992 [3].
To the best of our knowledge, there are 196 GOCs in the English literature [4][5][6][7][8][9][10][11][12][13][14]. Clinically, GOCs are small and usually appear as an asymptomatic swelling, though a few cases have presented with pain and paresthesia. The most common site is the mandible, particularly the anterior region. The cyst shows no sex predilection and mostly affects middle-aged individuals, between 45 and 50 years old; however, there are also reports in pediatric patients [4,15]. According to Kaplan et al. [16], its recurrence rate is around 35.9%, particularly when conservative surgical treatment is chosen.
Radiographically, it presents as a uni-or multilocular cystic lesion, with well-defined margins, though some lesions exhibit scalloped borders. Other findings include loss of cortical integrity, root resorption, and association with unerupted teeth [15]. Some cases show a dentigerous, lateral periodontal, and "globulomaxillary" relationship [17].
Microscopically, the diagnosis of GOC can be challenging, given the rarity of the lesion and the fact that the differential diagnosis includes benign and malignant lesions, such as botryoid cysts, surgical ciliated cysts, radicular or dentigerous cysts with metaplastic changes, and low-grade mucoepidermoid carcinoma (MEC) [14,16,17]. Histopathological features for the GOC have been described, but the exact microscopic criteria necessary for diagnosis have not been universally accepted. These features include a nonkeratinized stratified squamous lining epithelium with focal thickening (plaques) in the cystic lining, eosinophilic cuboidal or ciliated columnar cells, mucous cells, and interepithelial gland-like structures [1][2][3]16].
Several treatment modalities have been indicated for the GOCs, including conservative approaches, such as enucleation with or without curettage, marsupialization, peripheral ostectomy and chemical cauterization with Carnoy's solution, and marginal resection/partial jaw resection [4]. This report documents an uncommon case of GOC in a dentigerous relationship (GOC-DR), which was treated with enucleation and peripheral osteotomy.

Case Report
A 36-year-old male, with no medical history, was referred to the Clinical Hospital of the Federal University of Goiás, Goiânia, Goiás, Brazil, for evaluation of an asymptomatic radiolucent lesion in the posterior mandible region. Conebeam computed tomography (CBCT) scan showed a welldefined unilocular radiolucency associated with an impacted right third molar, extending to the distal root of the second molar, measuring 17 × 12 5 mm ( Figure 1). Intraoral examination revealed signs of healthy gingiva; absence of teeth 16, 36, 37, and 46; and absence of bone expansion. However, clinical attachment loss in the distal root of tooth 47 with pulp vitality was verified. Previous aspiration was negative and previous diagnosis of dentigerous cyst was made. Due to the small size of the lesion, the treatment choice included tooth removal, enucleation, and peripheral osteotomy. A thick cystic wall was evident during the surgical procedures.
The histopathological examination revealed cyst wall lining by nonkeratinized stratified squamous epithelium with varied thickness (Figure 2(a)). Duct-like structures surrounded by cuboidal cells and numerous mucous cells were also identified (Figures 2(b) and 2(c)). The superficial layer of the epithelium showed columnar ciliated and eosinophilic cuboidal cells, also called "hobnail cells" (Figure 2(d)).
Clinical diagnosis of GOC is challenging. The differential diagnosis includes radicular and dentigerous cysts, odontogenic keratocysts, and ameloblastoma. Although Krishnamurthy et al. [19] suggest that a preoperative aspiration biopsy may be helpful in diagnosing GOC, in our case, it was negative, as reported by Momeni Roochi et al. [23]. Distinct fluids have been reported in the literature, including clear with low viscosity, creamy high-viscosity, and brownish-red liquids [19,23,28,29]. Another interesting clinical finding in our case was the presence of a thick cystic wall, contrary to findings shown by Thor et al. [30].
The histopathological diagnosis of GOC also remains a challenge. Microscopic features include focal epithelial thickening, epithelial plaques, and glycogen-rich epithelial cells, which are also observed in botryoid and lateral periodontal cysts. The presence of ciliated epithelium and duct-like spaces with mucous cells and eosinophilic cuboidal cells located in the epithelial surface support the diagnosis of GOC [17,31]. According to Fowler et al. [17], the presence of microcysts, clear cells, and epithelial spheres may be helpful in distinguishing GOC-DR from dentigerous cyst with metaplastic changes. The most important and difficult distinction according to Kaplan et al. [16] is the differentiation of low-grade MEC from GOC, especially its multicystic variant. Ciliated cells, superficial cuboidal cells, epithelial whorls, and intraepithelial microcyst or duct-like structures are not typical for low-grade MEC, which can help in the differentiation. Immunostain for MASPIN, Ki-67, and CKs 18 and 19 may be helpful to distinguish GOC from lowgrade MEC [14]. Due to the overlapping of histological features with others lesions, Fowler et al. [17] suggested 10 microscopic parameters for diagnosing GOC: surface eosinophilic cuboidal cells or "hobnail cells", intraepithelial microcysts or duct-like spaces lined by a single layer of cuboidal to columnar cells, apocrine snouting of hobnail cells, clear or vacuolated cells, variable thickness in the cyst lining, papillary projections or "tufting" into the cyst lumen, mucous goblet cells, epithelial spheres, or plaque-like thickening cilia, and multiple compartments. According to the authors, the presence of seven or more microscopic parameters is highly predictive of a diagnosis of GOC. In our case, only multiple compartments and papillary projections were not evidenced.
Minor surgical procedures, such as enucleation with or without curettage and peripheral ostectomy, are the most common treatment modalities reported in the literature [4,32]. In this study, enucleation associated with peripheral osteotomy was performed due to three factors: patient choice, clinical and radiological diagnosis of a dentigerous cyst, and lesion size (17 × 12 5 mm). On the other hand, radical treatments, such as marginal resection, can sometimes be considered due to the biological behavior of GCO, particularly due to local aggressiveness and recurrence rates around 21-55% [15,19,33]. Some reports suggest that recurrence is more common in larger lesions, with cortical bone perforation and multilocular radiographic appearance [30,32]. In the present case, neither of these characteristics was evident and no recurrence was detected after two years follow-up.

Conclusion
This report describes an uncommon case of GOC-DR mimicking other lesions in the oral cavity. These lesions tend to most commonly affect the posterior mandible and younger male patients.   [25].