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Oncocytic sialolipoma of parotid gland: Case report and literature review


 Department of Pathology, Star Hospitals, Hyderabad, Telangana, India

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Date of Submission27-Mar-2021
Date of Decision17-May-2021
Date of Acceptance05-Jun-2021
Date of Web Publication06-Jun-2022
 

   Abstract 


Neoplastic lipomatous lesions of the salivary glands constitute ≤0.5% of all the salivary gland tumors. Oncocytic sialolipoma of the parotid glands is extremely uncommon. We report a case of oncocytic sialolipoma of the parotid gland in a 59-year-old male who presented with a gradually increasing swelling of the right parotid. Excisional parotid biopsy performed in view of possible pleomorphic adenoma as suggested on ultrasonography showed histological features consistent with oncocytic sialolipoma. We also described the characteristics of 24 previously reported cases of oncocytic sialolipoma of the parotid gland. The median age of the patients including the present case was 56 years (range 7–89), and 14 were male. The largest and the least reported sizes of the tumor were 7.0 and 1.4 cm, respectively. The left-sided parotid gland was more commonly involved (14/23). Despite its rarity, oncocytic sialolipoma should be considered in lipomatous parotid lesions showing epithelial components with oncocytic changes.

Keywords: Oncocytic lipoadenoma, oncocytic sialolipoma, parotid gland, sialolipoma


How to cite this URL:
Sureja VP, Tagore KR. Oncocytic sialolipoma of parotid gland: Case report and literature review. Indian J Pathol Microbiol [Epub ahead of print] [cited 2023 Jan 29]. Available from: https://www.ijpmonline.org/preprintarticle.asp?id=346694





   Introduction Top


Neoplastic lipomatous lesions of the salivary glands are uncommon, and constitute ≤0.5% of all the salivary gland tumors.[1] Based on the histology, these lesions are divided into monophasic lesions (lipoma) containing only adipose tissue, and biphasic lesions (where salivary epithelial components are seen in addition to the adipose tissue). The latter group is further categorized based on the type of epithelial components such as sialolipoma and oncocytic sialolipoma (also known as oncocytic lipoadenoma).[2] Oncocytic sialolipoma of the parotid glands is extremely uncommon with only 24 cases reported.[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14] Histopathology plays an important role in the diagnosis of these benign lipomatous lesions and differentiating them from malignant tumors. Here, we report a case of oncocytic sialolipoma of the parotid gland.


   Case Report Top


A 59-year-old hypertensive male presented with gradually increasing, painless swelling below the right ear for 6 months. The patient did not have fever, cold, cough, hemoptysis, xerostomia, odynophagia, dysphagia, weight loss, oral pain, facial weakness, or other symptoms of immunodeficiency.

The examination revealed a freely mobile, non-tender swelling of size 5 cm × 3 cm in the right parotid region. There was no cervical lymphadenopathy, and the rest of the physical examination was normal. The ultrasonography of the swelling suggested the possibility of pleomorphic adenoma. Based on these clinical and radiological findings, the patient underwent right superficial parotidectomy with facial nerve preservation. A well-circumscribed specimen of 5.5 cm × 3 cm × 2 cm was received for histopathological examination, which was yellow and tan-brown on cut section [Figure 1]a. The microscopic examination revealed a well-circumscribed encapsulated mass composed of mature adipose tissue admixed with epithelial components of the salivary gland [Figure 1]b and [Figure 1]c which constituted around 60% of the lesion. Around 80% cells of the epithelial component showed oncocytic differentiation [Figure 1]c and [Figure 1]d, having round to oval nuclei, prominent nucleoli, and eosinophilic granular cytoplasm. Periductal lymphocytic infiltrate [Figure 1]e and focal sebaceous differentiation of the ductal epithelium [Figure 1]f were also seen. There was no evidence of cellular pleomorphism, atypia, or mitotic activity. Lymphovascular, perineurial, or extracapsular invasion was not seen.
Figure 1: Oncocytic sialolipoma of the parotid gland. (a) Cut section of gross specimen. Histopathology showing (b and c) well circumscribed lesion with mature adipose tissue admixed with epithelial components of the salivary gland (c and d) oncocytic differentiation of the epithelial component (e) periductal lymphocytic infiltrate, and (f) focal sebaceous differentiation of the ductal epithelium

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   Discussion Top


Although lipoma is a very common soft-tissue tumor, salivary gland lipomatous lesions are uncommon.[1] There is no general agreement on the nomenclature and histologic classification of these lesions. Sialolipoma was not regarded as a separate entity until 2001 when Nagao et al.[15] proposed this term after studying seven cases of salivary gland lipomatous lesions. In contrast to lipoma (which contains only adipose tissue), sialolipoma additionally contains an epithelial component within the lesion.[2] The pathogenesis of sialolipoma remains unclear. It is suggested that the normal salivary gland component becomes entrapped within the proliferative adipose tissue.[16] Based on the presence of oncocytic changes (cells having eosinophilic granular cytoplasm) in the epithelial component of sialolipoma, these lesions are further categorized as “oncocytic lipoadenoma” by a few authors,[3],[4] and “oncocytic sialolipoma” by others.[10] Although it remains controversial, the latter terminology sounds more appropriate for these lesions as the epithelial component is non-neoplastic.[15] The recent World Health Organization classification of head and neck tumors has not yet adopted these terms, and irrespective of oncocytic epithelial changes, all the lesions are classified under sialolipoma.[1] The distribution of the adipose tissue and oncocytic epithelial component within a lesion greatly varies. Some lesions show intermingling of both the tissues, whereas circumscribed oncocytic nodules within the adipose tissue background are seen sometimes.[4] Although a few foci of oncocytic cells can also be seen in sialolipoma, it usually lacks a significant oncocytic component. Periductal inflammation and foci of sebaceous metaplasia are common features of both sialolipoma and oncocytic sialolipoma.[2]

Oncocytic sialolipoma of the parotid gland is extremely uncommon. PubMed search with terms “sialolipoma,” “lipoadenoma,” “oncocytic sialolipoma,” and “oncocytic lipoadenoma,” identified 24 cases of parotid gland oncocytic sialolipoma published in the English literature with adequate data.[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14] The characteristics of these cases including the present case is summarized in [Table 1]. The median age of the patients was 56 years (range 7–89), and 14 were males. The largest and the least reported size of the tumor were 7.0 and 1.4 cm, respectively. The left-sided parotid gland was more commonly involved (14/23).
Table 1: Published cases of parotid gland oncocytic sialolipoma

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The differential diagnosis for sialolipoma includes salivary gland lesions containing adipose tissue. Interstitial lipomatosis is an age-related change where the lesion is uncircumscribed as opposed to an encapsulated lesion in the sialolipoma. In fibrolipoma, mature adipose tissue is seen interspersed by dense connective tissue without a capsule. Spindle cell lipoma is composed of a well-circumscribed lesion containing bland spindle cells, collagen, and adipocytes. Pleomorphic adenoma can be identified by the proliferation of both the epithelial and stromal components and chondromyxoid stroma.[2],[6]

Despite the rarity of lipomatous lesions of the salivary gland, oncocytic sialolipoma should be considered in patients with parotid lesions having adipose tissue and epithelial components with oncocytic changes. Further studies are warranted to enhance the knowledge regarding the appropriate nomenclature/classification, clinical profile, pathogenesis, and prognosis of this uncommon entity.

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Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Naggar AK, Chan JKC, Grandis JR, Takata T, Slootweg PJ. WHO Classification of Head and Neck Tumors. 4th edi. Lyon: IARC; 2017.  Back to cited text no. 1
    
2.
Agaimy A. Fat-containing salivary gland tumors: A review. Head Neck Pathol 2013;7:90-6.  Back to cited text no. 2
    
3.
Lau SK, Thompson LDR. Oncocytic lipoadenoma of the salivary gland: A clinicopathologic analysis of 7 cases and review of the literature. Head Neck Pathol 2015;9:39-46.  Back to cited text no. 3
    
4.
Agaimy A, Ihrler S, Märkl B, Lell M, Zenk J, Hartmann A, et al. Lipomatous salivary gland tumors: A series of 31 cases spanning their morphologic spectrum with emphasis on sialolipoma and oncocytic lipoadenoma. Am J Surg Pathol 2013;37:128-37.  Back to cited text no. 4
    
5.
Chi CL, Kuo TT, Lee LY. Oncocytic lipoadenoma: A rare case of parotid gland tumor and review of the literature. J Pathol Transl Med 2015;49:144-7.  Back to cited text no. 5
    
6.
Mitsimponas KT, Agaimy A, Schlittenbauer T, Nkenke E, Neukam FW. Oncocytic lipoadenoma of the parotid gland: A report of a new case and review of the literature. Int J Clin Exp Pathol 2012;5:1000-6.  Back to cited text no. 6
    
7.
Chahwala Q, Siddaraju N, Singh N, Goneppanavar M, Basu D. Fine-needle aspiration cytology of oncocytic lipoadenoma of the parotid gland: Report of a rare case. Acta Cytol 2009;53:437-9.  Back to cited text no. 7
    
8.
Klieb HBE, Perez-Ordoñez B. Oncocytic lipoadenoma of the parotid gland with sebaceous differentiation. Study of its keratin profile. Virchows Arch 2006;449:722-5.  Back to cited text no. 8
    
9.
Kato M, Horie Y. Oncocytic lipoadenoma of the parotid gland. Histopathology 2000;36:285-6.  Back to cited text no. 9
    
10.
Ruangritchankul K, Connor S, Oakley R. Oncocytic sialolipoma of parotid gland: Case report and literature review. Head Neck Pathol 2019;13:548-53.  Back to cited text no. 10
    
11.
Ashraf MJ, Azarpira N, Anbardar MH, Hashemi SB. Oncocytic lipoadenoma of the parotid gland: Cytological findings and differential diagnosis on fine-needle aspiration. Diagn Cytopathol 2015;43:72-4.  Back to cited text no. 11
    
12.
Tokyol C, Dilek FH, Aktepe F, Ayçiçek A, Altuntaş A. Oncocytic lipoadenoma of the parotid gland: A case report with fine needle aspiration cytology findings. Kulak Burun Bogaz Ihtis Derg 2010;20:146-9.  Back to cited text no. 12
    
13.
Ilie M, Hofman V, Pedeutour F, Attias R, Santini J, Hofman P. Oncocytic lipoadenoma of the parotid gland: Immunohistochemical and cytogenetic analysis. Pathol Res Pract 2010;206:66-72.  Back to cited text no. 13
    
14.
Devadoss CW, Murugan P, Basu D, Jagdish S. Oncocytic lipoadenoma of the parotid gland: Report of a rare case. J Clin Diagn Res 2012;6:1076-8.  Back to cited text no. 14
    
15.
Nagao T, Sugano I, Ishida Y, Asoh A, Munakata S, Yamazaki K, et al. Sialolipoma: A report of seven cases of a new variant of salivary gland lipoma. Histopathology 2001;38:30-6.  Back to cited text no. 15
    
16.
Okada H, Yokoyama M, Hara M, Akimoto Y, Kaneda T, Yamamoto H. Sialolipoma of the palate: A rare case and review of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:571-6.  Back to cited text no. 16
    

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Correspondence Address:
Venu Patel Sureja,
Department of Pathology, Star Hospitals, Banjara Hills, Hyderabad - 500034, Telangana
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijpm.ijpm_323_21



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