Discussion
Dermoid cyst, epidermoid cyst and teratoma are three histologically closed uncommon lesions englobed in the concept of dermoid cyst [6]. These are nonodontogenic benign lesions. Dermoid cysts are found in the head and neck region in about 7% of all cases [4]. The intraoral ones are rare and account for less than 0.01% of all the cysts [2-5]. The floor of the mouth is the most commonly affected area araising in 23% of the head and neck dermoid cyst (sublingual dermoids) [9], as this is one of the sites of embryonic fusion [4].
However, these cysts can also be found less frequently in the tongue, lips, uvula, jaw bones and buccal mucosa [3,4].
The epidermoid cysts, which were firstly described by Rose in 1859, are the most common comprising 85-90% of all excised cysts (7,8). Epidermoid cysts are also known by a number of other names, including follicular cysts, epidermal inclusion cysts and wen [2,3].
A review of the literature was conducted on the database Medline via its interface PubMed using Mesh Keywords : “oral cavity”, “cyst, epidermoid”, “cyst, dermoid” and combining the following Boolean equations : “((cyst, epidermoid[MeSH Terms]) OR (cyst, dermoid[MeSH Terms])) AND (oral cavity[MeSH Terms]) ”, until december 2020. This bibliographic research concluded to 7 case reports about epidermoid cyst of the buccal mucosa from 6 articles. The parameters extracted from these cases were summarized in Table I and concerned: gender, age, onset, site and size.
According to this literature review, the two first cases of epidermoid cyst in the buccal mucosa were published by Schneider, Mesa in 1978, and involved women in the fourth decade of their lives [10].
In the same year (1978) Gutman et al. [11] reported an atypical case of intradermal nevus which appeared to involve the wall of an epidermoid cyst. The authors believed that the cyst comprised the major portion of the lesion, and originated independently of the associated nevus.
Epidemiologically, dermoid and epidermoid cysts may be present at birth and also in old patients, with the majority occurring in the second and third decades of life [2,9]. The mean age of included patients in this review was 33 years. The present case was a 56-year-old patient which seems to be an older age than that reported in most cases.
Even though that the frequency of occurrence is equal in both genders [9], kim et al. [12] reported that male were more affected than female, which was in consistent with present case. Regarding the patients with epidermoid cysts of the buccal mucosa, including our case, 4 were male and 4 were female.
Many etiopathogenetic theories have been proposed for the development of (epi)dermoid cyst. These can be conginetal or aquired [2,8]. Congenital cysts are dysembryogenetic lesions that arise from ectodermic elements, migrating into the facial midline, entrapped during the fusion of the first and second branchial arches between the 3rd and 4th weeks of intrauterine life [3,8,13]. According to the theory of acquired development, the epidermis migrates into the deep tissue as a result of a physical trigger such as trauma or surgical complication and develops into an (epi)dermoid cyst [14]. The posttraumatic cysts are also called as implantation keratinizing epidermoid cysts [2]. Ozan et al. [3] and Rajayogeswaran et al. [13] do not believe in this congenital theory for the appearance of the lesion in the buccal mucosa. Posttraumatic cysts are usually asymptomatic and may not be associated in the patient’s mind with any specific trauma, as this may be occurred several years earlier. For the present case, the patient is not sure if an injury occured before the appearance of the lesion.
The size of the cyst is variable from millimeters till some centimeters, depending on its first clinical manifestation [9]. This review reported that the size of epidermoid of the buccal mucosa is ranging from 10 mm to 40 mm.
There may be a left side predilection of the occurrence; as reported in the present case.
Swellings in the buccal mucosa may lead to a series of clinical diagnoses, as some conditions may present in a similar aspect making the diagnosis difficult.
The differential diagnosis of lesions occuring in the buccal mucosa with a clinical aspect similar to the present case include odontogenic infections affecting the facial spaces of buccinator and masseter muscles, pleomorphic adenoma, muccocele, cervical lymphadenopathy, hemongioma, lipoma, fibroma, neoplasms and dermoid cyst [4,8,9].
In the present case, odontogenic infection was ruled out as the lesion was not associated clinical symptoms such fever and malaise. Such the lack of nodal involvement, the slow progression of the lesion and its benign appearance, neoplastic conditions were excluded, as well.
To achieve the correct diagnosis and differenciate between vascular, salivary and mucosal lesions, specialised imaging techniques such as ultrasonography (US), computed tomography (CT), Magnetic Resonance Imaging (MRI) should be carried out [4]. On CT scans, the dermoid cyst appear as moderately thin walled, unilocular masses filled with a homogeneous, hypoattenuating fluid substance with numerous hypoattenuating fat nodules giving the pathognomonic “sack-ofmarbles” appearance [4]. On MRI the lesion appears as a well-circumscribed mass. The signal intensity of epidermoid cysts is high in T2-weighted images and low in T1-weighted images. US is interesting such is a non invasive, easy, quick and cheap test. US findings revealed a well-circumscribed, smooth mass with a heterogeneous interior [4]. In the present case, the US was useful in diagnosing the lesion on the buccal mucosa. Even the aspiration biopsy is commonly used; in many cases, it can result in a not reliable diagnostic sample [9]. Thereby, imaging plays an important role, but the definitive diagnosis is based on the histopathological findings.
The surgical excision or enucleation is the gold standard treatment via an intraoral or extraoral approach, depending on the size and the location of the cysts [9]. In all cases of this review, surgeries were performed. Recently, Mumtaz et al. [15] reported the first case of dermoid cyst in the floor of the mouth being managed with marsupialization, as a good option of large epidermoid cysts.
Although recurrences have been described as less than 3% [14], these may be prevented by the complete removal of the cyst wall. There is no recurrence in all included cases.
Despite the benign nature and the good prognesis of dermoid or epidermoid cysts [4] isolated cases of premalignant and malignant conditions (Bowen’s disease, Paget’s disease, and squamous cell carcinoma) have been reported. Bhatt et al. [7] described a case of a squamous cell carcinoma that appeared in the epithelium of an epidermoid cyst in the floor of the mouth, associated with the sublingual gland.
Table I : Review of the literature regarding epidermoid cysts arising in the bucal mucosa.