Salivary glands in the mouth produce saliva to aid food digestion, lubricate the bolus and oral cavity, initiate chemical digestion, and provide immune defenses [1]. Glands are clusters of secretory cells intermixed within the epithelial lining of tissues [1]. Since the salivary glands are exocrine, the secretory portions are invaginations of epithelium, called acini, that form ducts through which the secretions from the secretory cells may travel. Myoepithelial cells are the contractile units found at the base of and encase the secretory portions of glands [1, 2]. The actin and myosin-rich myoepithelial cells contract around acini to squeeze secretions into the ductal system [1].

There are two types of salivary glands: major and minor glands. The major glands are encased in a fibrous capsule, are paired, and include the submandibular, sublingual, and parotid glands. The minor salivary glands are more diffuse and numerous than the major salivary glands. They are found sporadically within the submucosal lining of the oral cavity and features.

Clusters of minor salivary glands are located around the labia, buccal region, palatoglossal region, and palate of the oral cavity [3]. In the second edition of Terminologia Anatomica, five minor salivary glands are listed, i.e., labial, buccal, palatine, molar, and lingual glands [4].

Molar glands are also called retromolar glands [5]. The buccal gland is a group of small glands near the area where the parotid duct pierces the bucinator. The labial and buccal glands are mixed, while those found deeper within the pharyngeal recesses are lined with relatively higher concentrations of mucous tubules [3, 6]. Ectopic minor glands are not frequently reported in the literature because their presence is highly variable and their functional contribution to saliva production is minimal compared to the major glands [3]. Though minor salivary glands generally are not responsible for much of the saliva production, the buccal glands are among the biggest contributors of the minor glands [7]. This case report will describe an accessory ectopic buccal gland found within the bucinator muscle.

During the histological observations of sections made through a cadaveric mandible (premolar and molar areas), an ectopic buccal gland was identified in the mandibular premolar area (Fig. 1). The cadaver specimen was from a female whose age at the time of death was 92 years. Masson-trichrome staining was used for slide preparation. The plane of the slide was a coronal section. The gland was located within the bucinator muscle nearby the mandibular origin of the bucinator. The size of the gland was approximately 1.2 mm×2.0 mm. Adjacent to this gland, a smaller gland was also found between the bucinator and the buccal mucosa. The ectopic gland was not found in other coronal sections of the molar area from the same cadaver.

Figure 1. Section of mandible stained with Masson’s trichrome stain. The ectopic buccal gland (yellow arrowheads) is within the bucinator (red arrowheads). The smaller gland is also seen between the bucinator and buccal mucosa (yellow arrow).

The present study was performed in accordance with the requirements of the Declaration of Helsinki (64th WMA General Assembly, Fortaleza, Brazil, October 2013). The authors state that every effort was made to follow all local and international ethical guidelines and laws that pertain to the use of human cadaveric donors in anatomical research [8].

Minor salivary glands have been described as “spontaneous secretors” [9]. These glands produce and release their secretions asynchronously, and it has been hypothesized that they can function independently of nervous stimulation. Given this, perhaps the finding of a minor salivary gland within muscle tissue would aid in its secretory function rather than disrupt the normal functioning of the gland. Thus, the mucous gland would be subject to the routine contraction of the bucinator.

Though minor salivary glands have not been extensively studied in humans, they have been well documented in other mammals, namely rodents. Rats have a major salivary gland called the anterior buccal gland anterior to the third molar [10]. The buccal gland found in murine models is purely mucous, which is thought to be due to differences in mesenchyme induction during development. The positioning of this gland is similar to the location of the accessory parotid gland, which is commonly found in humans [2].

There are few anatomical studies on the human buccal glands. According to Kamijo [11], the human buccal glands are always located on the lateral surface of the bucinator. However, others have stated they are between the buccal mucosa and the bucinator (i.e., medial to the bucinator).

The flow rate of the buccal glands is significantly lower in children than in adults [12]. In elderly individuals, the buccal glands as well as the labial glands might show a decreased, unstimulated salivary flow [12]. The flow of the buccal gland is higher than the labial gland [13].

Salivary glands derive from embryonic ectoderm and endoderm tissues [2]. Anatomical variations in exocrine glands, like the salivary glands, can result from congenital defects.

Developmental abnormalities are a result of aberrant invaginations of mesenchyme that are either too close or far from the still developing lymphatic tissue [14]. Such variations may result in ectopic glands—glands found in locations other than typical and with an associated duct system separate from the typical gland’s main duct system [14]. In the present case, the continuous contraction of the bucinator might cause chronic injury to the ectopic gland.

To our knowledge, the present case is the first histological evidence of an ectopic buccal gland within the bucinator muscle. Further studies are now necessary to discern the prevalence of such glands.

Conceptualization: RST, JI. Data acquisition: JI. Data analysis or interpretation: ERL. Drafting of the manuscript: ERL. Critical revision of the manuscript: AC, RST, JI. Approval of the final version of the manuscript: all authors.

No potential conflict of interest relevant to this article was reported.

The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind’s overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude [15].