Journal of Current Research in Scientific Medicine

CASE REPORT
Year
: 2021  |  Volume : 7  |  Issue : 2  |  Page : 131--134

Lipoma of parotid mimicking as pleomorphic adenoma


PA Pradeep Raj1, Mohammed Fazil1, David Livingston1, C Peter Manoharan1, Kevin Manuel2, Emil Phinehas1,  
1 Department of General Surgery, Pondicherry Institute of Medical Sciences, Puducherry, India
2 Department of Pathology, Pondicherry Institute of Medical Sciences, Puducherry, India

Correspondence Address:
P A Pradeep Raj
Department of General Surgery – Pondicherry Institute Of Medical Sciences, Puducherry
India

Abstract

Lipomas are the most common benign mesenchymal tumors, arising in any location where fat is normally present in the head-and-neck region in adults. Lipoma of parotid gland is rare, hence, not often considered for differential diagnosis for parotid swellings. When there is any suspicion, computed tomography, and magnetic resonance helps in confirmatory diagnosis. We present a 27-year-old man with a swelling in parotid gland, which was diagnosed as pleomorphic adenoma on fine-needle aspiration cytology. Surgical excision of parotid gland is the management even though excision is challenging because of the facial nerve, which courses through the parotid gland. The postoperative histopathology revealed a lipoma, the clinical picture, radiological, and histopathological features of this case is being discussed here.



How to cite this article:
Pradeep Raj P A, Fazil M, Livingston D, Manoharan C P, Manuel K, Phinehas E. Lipoma of parotid mimicking as pleomorphic adenoma.J Curr Res Sci Med 2021;7:131-134


How to cite this URL:
Pradeep Raj P A, Fazil M, Livingston D, Manoharan C P, Manuel K, Phinehas E. Lipoma of parotid mimicking as pleomorphic adenoma. J Curr Res Sci Med [serial online] 2021 [cited 2022 May 21 ];7:131-134
Available from: https://www.jcrsmed.org/text.asp?2021/7/2/131/334459


Full Text



 Introduction



Lipomas are the most common benign mesenchymal tumors, arising from the fat in the fifth to the sixth decades of life. Males are 10 times more affected than females.[1] Thirteen percent of these neoplasms arise in the head–and- neck region mainly in posterior triangle and forehead.[2] Lipomas of parotid generally occur in the seventh decade, whereas those in deep lobe have been reported to be highest in the fourth decade.[3],[4] The lipoma of parotid gland is a rare entity, comprising 0.6%–4.4% of all parotid tumors.[5] So far, more than 250 cases were reported. Because of their rarity, they are not often considered in the differential diagnosis of parotid tumors.

Parotidectomy is the management as excision is challenging because of the facial nerve, which courses through the parotid gland.[6] The preferred treatment is the complete surgical excision, which will minimize the possibility of a recurrence and will also lead to a definitive diagnosis. Here, we are describing a case of lipoma arising from deep lobe of the parotid gland that was successfully removed with no complication.[7]

 Case Report



A 27-year-old male had swelling in the right parotid region for 1 year. Nonpainful swelling insidious in onset, gradually progressive to attain the present size [Figure 1]. No fever, increase in size of the swelling, or difficulty while taking food. It was 6 cm × 4 cm, nontender with well-defined borders, soft in consistency, and lobulated. The swelling was obliterating the right retromandibular groove and angle of mandible, lifting the right ear perorally, there is no discharge noticed from parotid duct. Curtain sign was positive. There was no involvement of facial nerve.{Figure 1}

Ultrasonography neck and fine-needle aspiration cytology suggested pleomorphic adenoma. Contrast-enhanced computed tomography neck showed ill-defined nonenhancing fat density lesion involving deep lobe of the right parotid gland probably benign neoplastic etiology and possibility of lipoma was also suggested [Figure 2]. The patient was planned for total parotidectomy under general anesthesia.{Figure 2}

Operative procedure

Superficial lobe was found to be stretched over the lipomatous swelling of deep lobe. After identifying facial nerve trunk, total conservative parotidectomy was done. Lipomatous deep lobe was seen pushing facial nerve outward and bulging out through its branches. Deep lobe was removed after carefully preserving all branches of facial nerve [Figure 3]. Histopathology of the specimen showed encapsulated benign tumor composed predominantly of lobules of mature adipose tissue along with scattered serous salivary acini and normal ducts in the deep lobe – sialolipoma of right parotid [Figure 4]a and [Figure 4]b.{Figure 3}{Figure 4}

Postoperatively, the patient had mild neuropraxia of right facial nerve, which resolved completely with steroids [Figure 5].{Figure 5}

 Discussion



Lipomas are the most common benign mesenchymal encapsulated tumors histologically, similar to mature adipose tissue.[6] Histologically, lipoma resembles normal adipose tissue, but the presence of a fibrous capsule helps to distinguish them from normal simple fat aggregation.[7] Lipoma of the parotid gland has been encountered in clinical practice even though incidence is rare. They usually present as a painless, slow-growing, and freely movable parotid mass. The most common preoperative impressions of parotid swellings are Warthin's tumor, parotid cyst, and pleomorphic adenoma.[2] Janecka et al. described two true parotid lipomas, one of which involved the deep lobe of the parotid gland.[8]

Lipomas of deep parotid lobe sometimes may extend between the sternocleidomastoid and digastric muscles, causing an asymptomatic parotid region swelling. In some cases, they may extend to the parapharyngeal space, causing medial displacement of the lateral pharyngeal wall,[9] facial nerve involvement,[10] and pain[7] are uncommon.[6] Because of their rarity, they are not often considered in the differential diagnosis of parotid tumors.

The normal parotid gland is easily visualized on both computed tomography (CT) and magnetic resonance imaging (MRI). In case of lipoma of the parotid gland, the margin is clearly defined by MRI as a “black-rim,” enabling lipoma to be distinguished from surrounding adipose tissue, a distinction that cannot be made from CT images.[7] However, CT is preferred as it is cost effective.

Clinical examination alone is insufficient to identify the nature and location of deep parotid lipoma hence need radiological support.

In CT, normal parotid tissue reveals positive density, whereas lipomatous tissue will give negative attenuation (–50 to –150 Hounsfield units).[3],[9] In our case, the radiological opinion after CT scan was strongly in favor of lipomatous tumor of deep lobe of parotid gland.

Most authors suggest a formal superficial parotidectomy with full exposure of the facial nerve and its branches for deep parotid lobe lipomas.[10],[11],[12] Enucleation or excision of the well-encapsulated tumor with a rim of parotid gland tissue is another surgical approach and advocated for paraparotid or intraparotid lipomas.[8],[10],[13] In this study, we approached for superficial parotidectomy in view of pleomorphic adenoma, but intraoperatively, we found lipomatous tissue arising from deep parotid lobe so proceeded with total conservative parotidectomy.

 Conclusion



In this case report, although lipoma arising from parotid is rare, it should be considered among the differential diagnosis. Lipomas can be diagnosed preoperatively with a reasonable level of certainty with a proper history combined with radiological and histopathological findings. The preferred treatment as suggested in the literature for lipomas in the region of parotid is enucleation. Whereas sometimes in the case of intraparotid lipoma of deep lobeas described in this case report, total conservative parotidectomy can be considered as a treatment option.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their 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.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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