SRM Journal of Research in Dental Sciences

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 10  |  Issue : 1  |  Page : 12--16

Salivary gland tumors: An institutional experience


Jimsha Vannathan Kumaran1, Mariappan Jonathan Daniel1, Mithunjith Krishnan2, Sruthi Selvam1,  
1 Department of Oral Medicine and Radiology, Mahatma Gandhi Postgraduate Institute of Dental Sciences, Puducherry, India
2 Department of Conservative Dentistry and Endodontics, Indira Gandhi Postgraduate Institute of Dental Sciences, SBV University, Puducherry, India

Correspondence Address:
Jimsha Vannathan Kumaran
Department of Oral Medicine and Radiology, Mahatma Gandhi Postgraduate Institute of Dental Sciences, Gourimedu, Puducherry
India

Abstract

Introduction: Salivary gland neoplasm represents the most complex and diverse group of neoplasm of the head and neck. Their diagnosis and management are complicated by relative infrequency. Around 64%–80% are located in the parotid gland, 7%–11% in the submandibular glands, and the remainder being distributed between the sublingual (1%) and the minor salivary glands (9%–23%) throughout the oral cavity. Aim: The aims of this study were: (1) To assess the frequency of salivary gland tumor based on tumor type and anatomic location. (2) To correlate gender and age in different tumor type. (3) To correlate the location of benign and malignant tumors. Subjects and Methods: A retrospective study was made in the Department of Oral Medicine and Radiology from the period of January 2006 to December 2017. Data were collected from the archives maintained in the Department of Oral Medicine, and details of the patient include age, sex, and site of the tumor were obtained and confirmed with histopathological study and sent for statistical analysis. Results: Chi-square test was applied to find the distribution of malignant and benign tumors. The prevalence of salivary gland tumors in our study was 0.3%, and the benign: malignant ratio was 1:2.2, with the mean age of occurrence was 45.01 ± 16.3 years with slight overall female predominance and a male-to-female ratio of 0.7–0.9, respectively. Conclusion: The present study was a single-institutional experience where the analysis of 32 SGTs was carried out. Malignant tumors were more compared to benign. Among benign tumors, pleomorphic adenoma was the most common type. Among the malignant salivary gland tumors, mucoepidermoid carcinoma was the most common, followed by adenoid cystic carcinoma then ex-pleomorphic adenocarcinoma followed by low-grade polymorphous adenocarcinoma.



How to cite this article:
Kumaran JV, Daniel MJ, Krishnan M, Selvam S. Salivary gland tumors: An institutional experience.SRM J Res Dent Sci 2019;10:12-16


How to cite this URL:
Kumaran JV, Daniel MJ, Krishnan M, Selvam S. Salivary gland tumors: An institutional experience. SRM J Res Dent Sci [serial online] 2019 [cited 2019 Apr 23 ];10:12-16
Available from: http://www.srmjrds.in/text.asp?2019/10/1/12/254239


Full Text

 Introduction



Salivary gland tumors represent an uncommon heterogeneous group of neoplasms with complex clinicopathological behavior.[1] These are diverse group of neoplasms, and this constitutes about 0.5% of all cancers and 5% of head-and-neck malignancy. Around 64%–80% are located in the parotid gland, 7%–11% in the submandibular glands, and the remainder being distributed between the sublingual (1%) and the minor salivary glands (9%–23%) throughout the oral cavity.[2],[3] While tumors of the salivary glands can appear at any age, the maximum incidence is in the fourth decade of life for benign lesions and in the fifth decade for malignant tumors.[4],[5] The etiological agents of salivary gland cancers remain unclear, while most other head-and-neck cancers are strongly related to smoking and alcohol drinking, these do not play a role in the salivary glands. At present, there are two theories trying to elucidate the origin of malignant salivary gland tumors (SGTs). The more accepted of the two theories is the reserve cell theory, and this states that salivary gland neoplasms arise from a stem cell of the salivary duct system. The second and less accepted theory is the multicellular theory. This theory states that salivary tumors arise from differentiated cells along the salivary gland unit.[6],[7],[8]

The incidence of SGTs is claimed to be influenced by geographical and racial factors. Tumors of the salivary glands display one of the greatest diversities of histology among human cancers. According to the literature, SGTs are probably the most complex among human neoplasias, due to their broad histological spectrum resulting from a multiple tumor-cell differentiation, its cell arrangements and extracellular matrix synthesis produced by certain tumor cells. The World Health Organization (WHO) proposed the first histological classification of salivary gland tumors in 1972.[9] Due to advances in the understanding of the etiology and behavior of these tumors as well as their wide morphological diversity, the WHO published the third and last edition of this classification in 2005.[10]

A neoplasm in the parotid gland is statistically more likely to be benign than one arising in a minor salivary gland. Pleomorphic adenoma is the most common benign salivary gland tumor, and mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor; the diagnosis of the salivary gland tumor includes clinical examination, supported by complementary techniques such as magnetic resonance imaging, computed tomography (CT) alone or combined with sialography, and fine-needle aspiration biopsy. The combination of some of these techniques is able to offer a tentative diagnosis that must be confirmed by histopathological study. Diversities of phenomenology of tumors of the salivary glands such as diverse histological forms, unpredictable clinical behavior, and different opinions expressed by several workers of long experience of different aspects of these tumors; hence, the diagnosis and management of these tumors are considered to be little challenging. Efficacy of treatment of malignant salivary gland tumors is dependent upon stage, location, presence of perineural invasion, treatment modality, histologic type, and presence of regional invasion.[11]

Many studies have been performed in order to describe the epidemiology of benign and malignant salivary gland tumors. The incidence, prevalence, age, gender, anatomical distribution, and survival rates vary between different parts of the world. In India, overall incidence of SGTs can be ascertained from the cancer registry established by the Indian Council of Medical Research. However, the geographic area and population covered by these registries are small and perhaps unrepresentative of the Indian population. In addition, there is a limited published literature on SGTs in the Indian population.[12],[13]

The aim of this study was to carry out a survey of benign and malignant cases of major and minor salivary glands, reported to Mahatma Gandhi Post Graduate Institute of Dental Sciences, Puducherry, India, during the period of January 2006–December 2017.

 Subjects and Methods



A retrospective study was made in the Department of Oral Medicine and Radiology from the period of January 2006 to December 2017. Data were collected from the archives maintained in the Department of Oral Medicine, and details of the patient include age, sex, and site of the tumor were obtained and confirmed with histopathological study. There were 12,003 histopathological reports in that particular period. Only salivary gland tumors both benign and malignant were included in the study. Data were collected pertaining to the tumor type, location, age, and gender of the patients and sent for statistical analysis. The tumors were classified according to the WHO's histological typing of SGTs. The collected data were analyzed statistically and results obtained compared with existing studies in the literature.

 Results



During the period of January 2006–December 2017, a total number of 12,003 specimens received for histopathological examination. Out of which, 32 specimens were of SGTs. The Chi-square test was applied to find the distribution of malignant and benign tumors. The prevalence of salivary gland tumors in our study was 0.3%, and the benign: malignant ratio was 1:2.2 [Table 1] and [Graph 1]. In this 10-year study, SGTs were found in patients between the ages of 14 and 71 years with the mean age of occurrence was 45.01 ± 16.3 years with slight overall female predominance and a male-to-female ratio of 0.7–0.9, respectively [Table 2] and [Graph 2]. Malignant salivary gland tumor was present mostly in the palate and mandible and benign tumor in the parotid gland [Table 3] and [Graph 3]. In case of benign tumors, pleomorphic adenoma was common and among the malignant MEC was observed.{Table 1}[INLINE:1]{Table 2}[INLINE:2]{Table 3}[INLINE:3]

 Discussion



The salivary glands are the site of origin of various neoplasms. These salivary gland tumors are relatively uncommon tumors and represent <2% of all tumors in the body and 5% of all head-and-neck tumors. The prevalence of SGTs in our institution from January 2006 to December 2017 was 0.3%. The relatively low frequency of SGTs is the most likely reason for our review. Only a few recorded analysis of SGTs based on significantly large number of cases are published from India, and very little information is available on the tumors of the head and neck over the last two-three decades. The annual incidence appears to be higher in Western publications which may be because these were based on centralized treatment centers.

Among all the salivary gland tumors, in the present study, malignant salivary gland tumors were more compared to benign salivary gland tumors in the ratio of 1:2.2, respectively. Most of the other studies reported that benign tumors were more compared to malignant salivary gland tumors, as stated by Eglis et al., Das et al., and Ahmed et al.[14],[15],[16] Among benign tumors, pleomorphic adenoma was the most common type. Among the malignant salivary gland tumors, MEC was the most common followed by adenoid cystic carcinoma (ACC) and ex-pleomorphic adenocarcinoma followed by low-grade polymorphous adenocarcinoma. Similar case series was reported from Vuhahula, Ahmed et al.,[16],[17] and Nagarkar et al.[17],[18],[19] The clinical characteristics of MEC have proved to be difficult to predict, but correlations to tumor grade and stage have been reported. The histologic features most useful in predicting the aggressive nature of these tumors are (1) a minor cystic component (<20%), (2) tumor necrosis, (3) neural invasion, (4) cellular anaplasia, and (5) brisk mitotic activity.[20] In our case series, we reported with intermediate type of MEC that originated from the minor salivary glands which were common, and mainly the site of occurrence was from hard palate, retromolar trigone followed by major salivary glands including the submandibular gland. Histologic grade and tumor stage appear to have profound effects on survival. Aro et al. found a statistically significant difference in disease-free survival between low-grade MEC and intermediate high-grade MEC (P = 0.001).[21] The second most common malignant salivary gland tumor was ACC. Histopathologically, it can be categorized into three growth patterns – cribriform, tubular, and solid patterns. The most common histologic subtype is the cribriform type (44%), characterized by a “Swiss Cheese” pattern of vacuolated areas. In our study, only cribriform pattern of ACC was reported. The prognosis for the cribriform subtype is intermediate. The tubular subtype (35%) carries the best prognosis and is characterized by cords and nests of malignant cells.

Clinical feature was varying in each case, benign tumors mostly presented with painless swelling. Swelling with pain and ulceration was noted with short duration among malignant tumors. Central salivary gland tumor mainly from the posterior mandible was reported as an expansile swelling with pain. There was one case with soft-tissue growth clinically similar to the inflammatory soft tissue, but histopathologically, it turned out to be an ACC. Hence, the clinical presentation of these tumors was challenging. Yet another case of MEC reported with swelling, pain, and nasal regurgitation. No facial paralysis was reported, and one case of ACC was with perineural invasion. Bony destruction on CT scan and lymph node metastasis was noted in the intermediate type of MEC arising from the retromolar trigone. In another case, which reported with expansile lytic lesion in the body of the mandible, histopathologically, the diagnosis was MEC originating from odontogenic cyst.

The incidence of benign neoplasms was more in the fifth decade, whereas malignant neoplasms were seen more common in the sixth and seventh decades.[22] Furthermore, the present study also showed malignant SGTs are seen in older patients than with benign tumors which agree with most published reports. The youngest case was reported at the age of 14 and oldest case at the age of 71 with the mean age of occurrence of 45.01 ± 16.3 years. From age-wise distribution, benign tumors were noted in the age range from 8 to 71 years with the mean age of 39.5 years and mostly common in the fourth decade of life. Malignant tumors were noted in the age range of 18–71 years with the mean age of 48.5 years and common from fifth decade onward. With slight overall female predominance, male-to-female ratio was 0.7–0.9, and this finding is similar with the other reports.[23] However, few studies have reported more male predilection in SGTs.[24]

 Conclusion



The present study was a single-institutional experience where analysis of 32 SGTs was carried out. The findings of age, sex, site distribution, and pathologic features encountered in the study were in agreement with those studies reported from India and other parts of the world. Although the number of SGTs discussed in this study is small, the findings should contribute in better understanding of the disease. Only a few studies based on significantly large number of cases are published from India. As very little information is available on the tumors of the head and neck over the last two to three decades, prospective multicentric studies need to be carried out to better discriminate the influencing factors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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