Gingival salivary gland choristoma: An unusual case report.

The gingival salivary gland choristoma, a highly unusual tumor-like mass alteration constituted by normal salivary gland cells in an abnormal location, reported for the first time in 1964 by Moskow and Baden. To our knowledge, only 12 cases of this entity (including present case) are reported to date, the majority observed as asymptomatic, solitary, smooth-surfaced tumor-like masses, measuring 0.5-1.5 cm with no osseous involvement. This case involves a 38-year-old female, with a pink symptomatic polypoid nodule on the posterior mandibular alveolar ridge mucosa, measuring 6 mm in diameter where no osseous abnormalities are shown. An excisional biopsy was performed. Microscopically, the specimen was constituted by dense fibrous connective tissue containing mucous minor salivary glands, intraductal calcification and adipose tissue clusters. Furthermore, inflammatory infiltrate foci were seen. An immunohistochemical technique was used as the support for the diagnostic methodology. The diagnosis of gingival salivary gland choristoma was established. Some development theories are discussed, referring to a pluripotential capacity of the gingiva. This case reflects the importance of not underestimating innocuous lesions that could represent more serious or unusual entities. In addition, histopathological analysis is mandatory to achieve a correct diagnosis and management of soft-tissue enlargements of oral mucosa. Copyright:

INTRODUCTION

The gingival salivary gland choristoma (GSGC) is a very unusual salivary gland alteration, described for the first time in 1964 by Moskow and Baden.[1] The term choristoma is defined as a cohesive tumor-like mass constituted by normal cells in an abnormal location.[23] To our knowledge, only 12 well-documented cases of GSGC (including present case) are reported to date [Table 1].[1456789101112] Other similar alterations have been reported and classified as gingival cyst derived from the ectopic salivary gland tissue. Although these entities present variations from the original case, the majority of GSGC are reported as asymptomatic, solitary, smooth-surfaced tumor-like masses, measuring 0.5–1.5 cm in diameter where no osseous involvement was observed.[2] In order to support for the diagnostic methodology, an immunohistochemical technique was applied. The purpose of this case report is to present the discovery of an unusual alteration of salivary gland development where it is liable to give an erroneous diagnosis, due to the clinical appearance and the location of this entity. In addition, the possible origin of the pathology is discussed.

Table 1

Gingival salivary gland choristomas reported to date

Author/year	Age (years)	Gender	Region	Histopathologic findings
Traeger[4]/1961	19	Male	Posterior maxilla	Gingival cyst and lobule of mucous salivar gland
Moskow and Baden[1]/1964	35	Male	Posterior maxilla	Mucous and sebaceous salivary gland and lipoid material
Moss-Salentijn and Applebaum[5]/1972	N/A	N/A	Posterior mandible	Mucous salivary gland
Wilson and MacEntee[6]/1974	77	Male	Anterior mandible	Papillary cystadenoma and lobule of mucous gland
Izumi et al.[7]/1976	11 months	Female	Anterior maxilla	Cystic glandular epithelium
Ide et al.[8]/1983	9	Female	Anterior maxilla	Mucous salivary gland and excretory ducts
Moskow and Baden[9]/1986	N/A	N/A	Anterior mandible	Mucous salivary gland and gingival cyst
Brannon et al.[10]/1986	21	Male	Anterior mandible	Mucous salivary gland
Ledesma-Montes et al.[11]/1998	43	Female	Posterior mandible	Mucous salivary gland
Gheena et al.[12]/2011	45	Female	Anterior mandible	Serous salivary gland lobules
Gheena et al.[12]/2011 (two cases)	51	Male	Anterior maxilla	Mucous salivary gland lobules
Present case	43	Female	Posterior mandible	Mucous salivary gland, adipose tissue and focal ductal calcification

N/A: Not avaliable

CASE REPORT

A 38-year-old female, was referred to the oral medicine service at the University of Guadalajara. At the diagnosis interrogation, the patient reported a 3-month symptomatic enlargement and did not mention any antecedents of importance. After obtaining consent from the patient, we proceed to intraoral exploration that revealed a polypoid nodule of approximately 6 mm in size, with smooth surface, firm consistency and similar coloration to the normal adjacent oral mucosa, the lesion was located on the posterior alveolar ridge mucosa close upon a root remnant of the mandibular right second molar [Figure 1a]. A periapical radiography was applied, where no osseous or dental root abnormalities are shown [Figure 1b]. An excisional biopsy was performed under local anesthesia, and the obtained tissue was submitted to the histopathological analysis.

Figure 1

Clinical and radiographic images. (a) A pedunculated swelling on the mandibular region close to root remnant of the second molar. (b) A periapical radiography where no bone involvement was noted

Microscopically, the specimen was constituted by a nodular mass of dense fibrous connective tissue [Figure 2], containing mucous minor salivary glands [Figure 3a], medium caliber arteries and lymphatic vessels. Adjacent to salivary acini, intraductal calcification [Figure 3b] and adipose tissue clusters [Figure 3c] could be observed. In the overall stroma, mild inflammatory infiltrate foci with predominance of lymphocytes were observed.

Figure 2

Photomicrography of the excisional specimen. Low-power view of the nodule, which is composed of connective and salivary gland tissue, the proliferation is lined by a keratinized stratified squamous epithelium (H and E, ×7)

Figure 3

Representative photomicrographs of the excisional specimen. (a) Between the stroma, multiple mucous cells are observed in the salivary gland lobes, also intralobular ducts, vascular spaces and lymphatic capillaries (H and E, ×80). (b) Next to the salivary gland lobes, intraductal calcifications are shown (H and E, ×80). (c) Presence of mature adipose tissue (H and E, ×80)

Although it is not necessary to establish the diagnosis, an immunohistochemical technique was performed to assess the proliferative activity of gland cells through the evaluation of Ki-67 expression, where it was observed that the majority of glandular cells show lack of expression [Figure 4]. In addition, positive expression of Ki-67 was found in the 2% and 4% of the nuclei of acinar and stromal cells, respectively. Based on the clinical and histopathological findings, the diagnosis of GSGC known as heterotopic salivary gland tissue was established. After the excisional biopsy, postsurgical care was indicated to the patient. The relief of occasional pain was achieved, and there was no recurrence after 12 weeks of follow-up.

Figure 4

Immunohistochemistry of Ki-67 staining (×400). Expression of Ki-67 in some stromal and acinar cell nuclei was observed (Ki-67, ×400). Inset: Internal positive control of the basal cell layer (×400)

DISCUSSION

According to the clinical and radiographic findings, this injury can be diagnosed with a reactive origin tumor-like mass due to the close relationship of the alveolar ridge with the occlusal contact, similar to an irritation fibroma, which usually is a well-delimited smooth surface where a firm consistency is observed on the nodule. This can vary from millimeters to a few centimeters and the growth is attached to the mucosa by a sessile or pedunculated base, and mild symptomatology can be associated due to constant trauma.[13]

According to the data, it is uncertain how minor salivary glands cells have interacted to create mucinous acini in the mandibular alveolar ridge. Researches explain some theories about the mechanism of the development of GSGC. One of these theories describes that the gingival epithelium shows a pluripotential quality, so the unusual location of this minor salivary gland tissue demonstrates that there is an ectopic formation, thus creating a morphogenesis of minor salivary glands.[8] Therefore, the fact of finding adipose tissue in the present case reinforces the possible theory of the pluripotential capacity of the gingiva. Another theory debates that in the normal salivary gland tissue development, a fraction of glandular tissue placed in the oral mucosa becomes “trapped” in the gingiva and consequently producing an ectopic growth, leading to the formation of GSGC.[2]

In general, it is known that the choristoma is a mature tissue growth with no significant mitotic activity. In the present case, we found positive Ki-67 in some acinar cells. There are a few studies that evaluate index proliferation in adult salivary glandular tissue. In one study, Ki-67 positive cells were expressed in acinar and ductal cells, with a frequency of 8% and 1%, respectively.[14] In a more recent work, Aure et al. evaluated the proliferative capacity of the salivary glands in murine mice. They found that homeostasis and maintenance of the adult salivary gland cells are through the duplication of differentiated secretory cells.[15]

CONCLUSION

The gingival mucosa is constantly under chronic irritation, chewing forces, trapped food remains, poorly-adjusted restorations, dental calculus, as well as the oral microbiota which under atypical conditions may become pathogenic. That is why in gingiva, there is a tendency for multiple entities to appear which are associated with chronic trauma and external irritation and could be a factor to present symptomatology. It is important that the professional of oral care do not underestimate the innocuous lesions, even polypoid nodules could represent more serious or unusual entities. Whereby a histopathological analysis is mandatory to achieve a correct diagnosis and management of soft-tissue enlargements of oral mucosa.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed

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Conflicts of interest

There are no conflicts of interest.