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An Official Publication of the Indian Association of Oral and Maxillofacial Pathologists

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Year : 2023  |  Volume : 27  |  Issue : 5  |  Page : 41-44

Oncocytoma of the parotid gland: A rare benign tumour

Department of Oral Pathology and Microbiology, Faculty of Dental Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Date of Submission15-Dec-2021
Date of Acceptance08-Sep-2022
Date of Web Publication04-Feb-2023

Correspondence Address:
Akhilesh Chandra
Assistant Professor, Department of Oral Pathology and Microbiology, Banaras Hindu University, Varanasi, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jomfp.jomfp_437_21

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Oncocytomas are one of the infrequent neoplasms seen in the oral cavity accounting for less than 2% of all neoplasms in the oral cavity with less than 1% chance of malignant transformation. They affect the major salivary glands and have a female predilection. The cognisance of the unique clinical and histopathological features is very important to conclude a confirmatory diagnosis. This paper reviews a case of oncocytoma presented in our department and also elucidates the diagnostic criteria for the same.

Keywords: Granular, oncocytes, oncocytoma, oxyphilic adenoma, salivary glands

How to cite this article:
Singh J, Chandra A, Srilatha T, Jain T, Raja D, Agrawal R. Oncocytoma of the parotid gland: A rare benign tumour. J Oral Maxillofac Pathol 2023;27, Suppl S1:41-4

How to cite this URL:
Singh J, Chandra A, Srilatha T, Jain T, Raja D, Agrawal R. Oncocytoma of the parotid gland: A rare benign tumour. J Oral Maxillofac Pathol [serial online] 2023 [cited 2023 Mar 21];27, Suppl S1:41-4. Available from: https://www.jomfp.in/text.asp?2023/27/5/41/369182

   Introduction Top

Oncocytoma is a rare benign salivary gland tumour composed of large epithelial cells known as oncocytes. These are predominantly composed of oncocytic cells lining the salivary ducts. The prefix onco is derived from the Greek word onkoustai, which means to swell.[1] The term 'Oncocytoma' was proposed by Jaffe. Meza-Chavez later proposed the term 'Oxyphilic granular cell adenoma', ascribed to the eosinophilic granular cytoplasm of tumor cells, due to increased numbers of mitochondria.[2]

Oncocytes are uncommon in younger than 50 years of age but it is usually found in all individuals by age 70 years in the salivary glands. Apart from the major salivary glands in the oral cavity, oncocytes are also found in a great number of locations in the body such as respiratory tract, mammary glands, thyroid gland, pancreas, parathyroid gland, pituitary gland, testicle,  Fallopian tube More Details, liver and stomach. The first case of Oncocytoma in the salivary gland was identified by Hamperl in 1931.[3] In kidneys, they were identified by Klein and Valensi in 1936.[4]

Oncocytoma is a tumour of the major salivary gland mainly affecting the parotid gland. It is usually seen in the seventh to eighth decade of life with a slight female predilection.[5] It is a benign, unilateral, painless, slow growing, solitary tumour.[6] In the salivary glands, they account for less than 2% of all neoplasms with less than 1% chance of malignant transformation.[7] Fine needle aspiration cytology alone cannot diagnose an oncocytoma, thus CT scan and MRI along with detailed histopathological examination are required to diagnose this infrequent neoplasm. The aim of this case report is to present a case of Oncocytoma and to compare its clinical, radiographic and histopathological features with the other cases available in the literature; thus, significantly add to the same.

   Case Report Top

A 73-year-old male patient reported a chief complaint of a round fibrous swelling over the right parotid region for the last 35 years. The swelling gradually progressed to the current size. The patient had no significant history of any habit. The patient's family history was non-contributory. Extraoral examination revealed facial asymmetry due to the swelling [Figure 1]. The swelling extended anteroposteriorly from the ramus to the auricle region. Superiorly, it extended from the inferior orbital margin to the inferior border of the mandible covering the entire parotid gland region. Lymph nodes were palpable, mobile and soft in nature. There were no significant intraoral findings [Figure 2]. Based on the clinical and radiographic findings, a provisional diagnosis of Pleomorphic Adenoma was given. The lesion was surgically excised and sent for histopathological examination.
Figure 1: Patient having extraoral facial asymmetry

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Figure 2: No intraoral changes

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On gross examination, two soft tissue specimens were received, roughly measuring approximately 5.0 × 2.5 cm and 3.0 × 2.5 cm in size. The soft tissues were grey in color, irregular in shape and firm in consistency. The cut surface of the larger bit was greyish red in color [Figure 3]. Both the soft tissue specimens were sectioned and two bits from each specimen were taken out for routine processing. The rest of the specimen was preserved.
Figure 3: Gross specimen received

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The histopathological examination revealed a partially encapsulated salivary gland architecture and minimal connective tissue stroma. Low power view showed sheets of large polyhedral cells (oncocytes), with abundant granular, eosinophilic cytoplasm arranged in a glandular pattern [Figure 4]. The cells have centrally located hyperchromatic nuclei [Figure 5]. The connective tissue stroma is scant, seen in the form of thin fibrous septa. The connective tissue also shows lymphocytic infiltration along with vascular spaces lined by endothelial cells and a few areas of extravasated RBCs. On the basis of histopathological features, a final diagnosis of 'Oncocytoma' was given.
Figure 4: Photomicrograph of the histopathological section revealing sheets of large polyhedral cells arranged in a glandular pattern in minimal connective tissue stroma (H&E, X20)

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Figure 5: Photomicrograph of the histopathological section revealing sheets of oncocytes with granular cytoplasm with a large vesiculated nucleus and prominent nucleoli (H&E, X40)

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   Discussion Top

Oncocytoma is a very rare salivary gland neoplasm accounting for less than 2% of all salivary gland tumours.[7] It is a tumour of the major salivary gland affecting individuals in seventh to eighth decade with a slightly greater female predilection (Hamperl, 1931).[3] However, Synderman and Suen in the year 1986 observed that there was no sex predilection.[8] The lesions are smaller in size, usually not exceeding more than 4 cm.[1] These are unilateral, painless tumour of the salivary gland affecting the salivary ductal cells.

The oncocytic lesions of the ductal and acinar elements of salivary glands were described as 'granular swollen cells' by Schaffer nearly a century ago.[9] In 1927, McFarland described this tumor as an 'adenoma', without explicitly calling it an oncocytoma.[10] The term 'Oncocytoma' was proposed by Jaffe in 1932. Meza-Chavez later proposed the term 'Oxyphilic granular cell adenoma' in 1949. The term oxyphilic granular cell adenoma was proposed due to a diffuse granular appearance of the cytoplasm of the tumour cells which is attributed to the eosinophilic granular cytoplasm, due to increased numbers of mitochondria.[2]

Oncocytoma is a well-circumscribed tumour that is composed of sheets of large polyhedral cells with abundant granular, eosinophilic cytoplasm.[1] These polyhedral cells are the oncocytes. These cells are sometimes arranged in a glandular or alveolar pattern. The nuclei of these cells are large, hyperchromatic and are placed centrally. Sometimes one can also see the vesicular nucleus as seen in our case. The cells are eosinophilic and granular in appearance. The granularity of these cells can be attributed to the abundant mitochondria present. The stroma is scanty often seen in the form of thin fibrovascular septa.[1] A lymphocytic cell infiltrate is seen in these lesions but does not form an integral part of them.[5] Ultrastructural studies of parotid oncocytomas by Tandler and associates and Kay and Still have shown that the cells are engorged with enlarged and morphologically altered mitochondria.[5] All these features were present in our case.

The histological differential diagnosis of Oncocytoma includes Warthin's tumor, Acinic cell carcinoma, Clear cell carcinoma, Oncocytic carcinoma, Mucoepidermoid carcinoma and Metastatic renal cell carcinoma.[9] The characteristic histological features of these lesions are described in [Table 1].
Table 1: Histological differential diagnostic characteristics

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   Treatment Top

Oncocytomas are best treated by surgical excision with a small margin of normal surrounding tissue. In the parotid gland, this usually involves partial parotidectomy to avoid violation of the tumor capsule.[1] The facial nerve should be preserved whenever possible. In the submandibular gland, the entire gland should be removed. The prognosis after removal is good, with a low rate of recurrence apart from oncocytic carcinomas. However, a recurrence rate of approximately 20% has been reported due to incomplete surgical eradication or occult multifocality.[11]

   Conclusion Top

Oncocytomas have unusual histopathologic features which should be probed in depth before diagnosing any such neoplasm. Even though oncocytomas have a low recurrence and good survival rate, these lesions also demand an apt diagnosis. This case report elucidates the importance of the histologic diagnosis of any neoplasm apart from their routine clinical and radiographic diagnosis and also how an oral pathologist could help better in diagnosing a lesion of the head and neck with explicit microscopic features. Additionally, owing to the lack of large series, an industrious study of the cases reported in the literature may lead to a better understanding of this rare entity.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given his consent for his images and other clinical information to be reported in the journal. The patients understand that their names and initials 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.

   References Top

Neville BW, Damm DD, Allen CM, Bouquet JE. Oral and Maxillofacial Pathology. 2nd ed. Philadelphia: W.B. Saunders; 2001.  Back to cited text no. 1
Shahi S, Bhandari TM, Thapa PB, Shrestha D. Buccal oncocytoma: Report of a case and literature review. Annals Med Surg 2019;43:82-4.  Back to cited text no. 2
Hamperl H. Benign and malignant oncocytoma. Cancer 1962;15:1019-27.  Back to cited text no. 3
Klein MJ, Valensi QJ. Proximal tubular adenomas of kidney with so-called oncocytic features. A clinicopathologic study of 13 cases of a rarely reported neoplasm. Cancer 1976;38:906-14.  Back to cited text no. 4
Rajendran R. Benign and malignant tumors of the oral cavity. In: Rajendran R, Sivapathasundaram B, editors. Shafer's Textbook of Oral Pathology. 6th ed. Amsterdam: Elsevier; 2009. p. 169-73.  Back to cited text no. 5
Palmer TJ, Gleeson MJ, Eveson JW, Cawson RA. Oncocytic adenomas and oncocytic hyperplasia of salivary glands: A clinicopathological study of 26 cases. Histopathology 1990;5:487-93.  Back to cited text no. 6
Barnes L, Eveson JW, Reichart P, Sidransky D, editors: World Health Organization Classification of Tumours. Pathology and Genetics of Head and Neck Tumours. IARC Press: Lyon, 2005.  Back to cited text no. 7
Kochhar L, Kumar S, Deka RC, Bose S. Oncocytoma of the minor salivary glands of hard palate. Indian J Otolaryngol 1990;42:132-33.  Back to cited text no. 8
Palakshappa SG, Bansal V, Reddy V, Kamarthi N. Oncocytoma of minor salivary gland involving the retromolar region: A rare entity. J Oral Maxillofac Pathol 2014;18:127-30.  Back to cited text no. 9
[PUBMED]  [Full text]  
Manjunath SM. Oxyphilic adenoma involving floor of the mouth: A case report. Ann Essen Dent 2011;3:68-70.  Back to cited text no. 10
Mandel L, Carrao V. Bilateral parotid diffuse hyperplastic oncocytosis: Case report. J Oral Maxillofac Surg 2005;63:560-62.  Back to cited text no. 11


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1]


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