A study on the morphological spectrum of salivary gland tumors

Introduction: Salivary gland neoplasm are relatively uncommon and are constitute about 3% of all head and neck neoplasm. Atleast 80% of tumors are located in the parotid gland and the remaining tumors are located in submandibular, sublingual and in minor salivary glands. Objective: The aim is to identify the occurrence of various salivary gland tumors and to categorize them as per WHO classification. Further to identify the histomorphological patterns of salivary gland tumors. Materials and Methods: The biopsy and excised specimens of salivary gland tumors were received in the department of pathology. A gross examination of biopsy and excised specimen was carried out. All the biopsy specimens were well fixed in 10% buffered formalin, processed, embedded with paraffin. After the paraffin blocks were sectioned and stained with Haematoxylin-Eosin, special stains like PAS, Mucicarmin were applied to the sections where ever indicated. The stained slides were examined for histomorphological patterns of salivary gland neoplasms and categorized as per WHO classification. Result and Conclusion: A total of 57 salivary gland tumors specimens were included in the present study. The study report revealed that 40 cases were belong to benign making it 70.2% and the remaining 17 were malignant making it to 29.8% of the total Salivary gland tumors. Pleomorphic Adenoma was the most commonly observed benign tumor. Out of 40 benign tumors 33 were Pleomorphic adenoma (82.5%). Mucoepidermoid carcinoma was the most commonly observed malignant tumor. Out of 17 malignant tumors 6 were Mucoepidermoid carcinomas (35.2%) of all the malignant tumors. © 2020 Published by Innovative Publication. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by/4.0/)


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) salivary gland tumors account for more than 35 distinct variants. 3 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 * Corresponding author. E-mail address: margitheresa@gmail.com (J. M. Theresa).
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. scan of the patients were also reviewed and documented.

Methods
Formalin fixed biopsy and excised specimens of salivary glad neoplasms received from hospital were studied macroscopically. The tissues were routinely processed in to paraffin embedded blocks. Microscopic sections were taken and stained with Haematoxylin & Eosin. Special stains PAS and Mucicarmin were also used to stain the sections as and when required.

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  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

Discussion
Salivary gland tumors exhibit a diverse group of benign and malignant tumors which showed multifaceted clinical pictures, different morphological architecture with unpre-   16 Shashikala et al. 17 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, 18 Lakshmibai B Mallappa et al, 19 Maj T Chatter Jee et al, 20 Kirti N Jaiswal et al 21

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.