A study on the morphological spectrum of salivary gland tumors:

Introduction

Three pairs of major salivary glands are there in the oral cavity, which consist of parotid, submandibular and sublingual glands. Apart from these, other minor salivary glands are also in the oral cavity located in the floor of mouth, hard and soft palate, tonsil, tongue and oropharynx.1 Salivary gland neoplasms are rare, and are account for about 3-10% of head and neck neoplasms.2 As per the WHO revised classification (2017)3 salivary gland tumors account for more than 35 distinct variants.4 Keeping this in mind the present study is planned to analyze the morphological pattern and the spectrum of salivary gland tumors in this local population to understand and to correlate the variants of salivary gland neoplasms in our area.

Materials and Methods

The present study is a retrospective and prospective study on salivary gland tumors, and was carried out in the department of Pathology for a period of five years between August 2012 and 2017. The study was conducted on biopsy and excised specimens of salivary gland tumors. A total number of 57 cases of Salivary gland tumors were included is this study. Institutional Ethics Committee approval was obtained. Required data like clinical history, duration of symptoms, location of tumors, and other relevant details such as age, gender, and social status use of tobacco were obtained from the patients. Other results such as radiological examination like X–ray, Ultrasound and CT scan of the patients were also reviewed and documented.

Results

Among the 57 cases of Salivary gland tumors, histopathological reports revealed that 40 of them were benign neoplasm (70.2%) and the other 17 were malignant (29.8%) showed in Table 1.

On the basis of histomorphological features, the benign salivary gland neoplasms were further classified in Pleomorphic adenoma, Warthin’s tumor, Basal cell adenoma and Myoepithelioma. We observed that the most common benign salivary gland tumor was pleomorphic adenoma, which is seen in 33 cases (82.5%) followed by warthin's tumor which is seen in 3 cases (7.5%). The details of the number of cases in each type is shown Table 2.

Similarly, on morphological examination we could able to identify the histological variants of malignant salivary gland tumors as Mucoepidermoid carcinoma, Adenoid cystic carcinoma, Polymorphous low grade adenocarcinoma, Carcinoma ex pleomorphic adenoma, Basal cell adenocarcinoma and Salivary duct carcinoma. Among these, the most common malignant salivary gland tumor identified is mucoepidermoid carcinoma, which is seen in 6 cases (35.2%) followed by adenoid cystic carcinoma seen in 5 cases (29.4%). The details of the number of cases in each type is shown Table 3.

The most commonly involved salivary gland among the benign tumor is parotid gland. Out of 40 benign tumors 29 were observed in parotid gland. Similarly submadibular salivary gland involved by 7 benign tumors. It is observed that the least commonly involved salivary gland is minor salivary glands. The details of the number of cases in each type is shown Table 4.

The most commonly involved salivary gland by the malignant tumors is parotid gland. Out of 17 malignant tumors 13 were observed in parotid gland. However minor salivary gland was involved by 3 cases of malignant tumor. The least commonly involved salivary gland is the sublingual gland. Details of the number of cases in each type is shown Table 5. The most common benign and malignant salivary gland neoplams were pleomorphic adenoma and mucoepidermoid carcinoma which is shown below.

The following Haematoxylin and Eosin stain show the microscopic features of Pleomorphic Adenoma shown Figure 1.

Figure 1

Haematoxylin and eosin stain of pleomorphic adenomaSalivary gland Tumor Magnification: 100X)

The following Haematoxylin and Eosin stain show the microscopic features of Low grade Mucoepidermoid carcinoma shown Figure 2.

Figure 2

Haematoxylin and eosin stain of low grade mucoepidermoid carcinomaSalivary gland Tumor Magnification: 100X)

Discussion

Salivary gland tumors exhibit a diverse group of benign and malignant tumors which showed multifaceted clinical pictures, different morphological architecture with unpredictable prognostic status. Salivary gland tumors account about 0.4-13 per 1,00,000 patients per year.5 Among this 70-80% of tumors arises from parotid gland. Among them only 15-30% are malignant and the remaining are benign tumor. The most common benign tumor of parotid gland is Pleomorphic adenoma, and the most common malignant tumor is Mucoepidermoid carcinoma. About 50% of tumors that arising from minor salivary glands are malignant.6 Mucoepidermoid carcinoma, Adenoid cystic carcinoma and Polymorphous low grade adenocarcinoma are more common malignant tumors of minor salivary gland.7 The present study was carried on 57 consecutive cases of various types of salivary gland neoplasms. Out of the 57 salivary gland tumors studied, 40 were benign making it 70.2% and 17 were malignant making it to 29.8% of the total salivary gland tumors. The result observed in the present study is in correlation with Janudevi et al,8 Juan Araya et al,9 Rajesh Sing et al,10 M.S Gill et al,11 Alpana Banerjee et al,12 Nepal et al,13 irrespective of total number of cases. The details of the number of cases in each type is shown Table 6.

The benign lesions were more common than the malignant lesions. Pleomorphic Adenoma was the most commonly observed benign tumor. Of the 40 benign tumors 33 were Pleomorphic adenomas making it 82.5% of all the benign tumors. Similar observations were quoted by Shahidaniazi et al,14 Shilpa H Gandhi et al,15 Shafkat Ahrnad et al.16 Mucoepidermoid carcinoma is the common malignant tumor observed in the present study. Out of 17 malignant tumors 6 were Mucoepidermoid carcinoma (35.2%). Similar observations were quoted by Khandekar et al17 Shashikala et al.18 Present study showed that the neoplastic lesions affected salivary gland was parotid gland followed by submandibular salivary gland and other minor salivary glands. Among the 57 salivary gland tumors encountered in this study it is observed that 42 cases involve the parotid gland (73.6%) and 8 cases were involve submandibular gland (14.3%). The results also showed that the sublingual and minor salivary gland are the least affected. These findings are comparable with the results of other studies quoted by Krishnaraj Subhashraj et al,19 Lakshmibai B Mallappa et al,20 Maj T Chatter Jee et al,21 Kirti N Jaiswal et al22 and Subhashini Bandar et al.23

Conclusion

The present study results conclude that salivary gland neoplasms exhibit a varied histomorphological patterns. The most commonly observed benign and malignant salivary gland neoplasms are pleomorphic adenoma and mucoepidermoid carinoma. Limitations of this study include a limited number of available cases of each tumor type and therefore missing of some tumor types may be due to its relatively infrequent occurrence.

Source of funding

None.

Conflict of interest

None.