|Year : 2014 | Volume
| Issue : 4 | Page : 450-453
Pleomorphic adenoma of the parotid gland with cystic degeneration: A rare case report
Preeti Dhir1, Chaya M David2, Keerthi G Dhaduti3
1 Department of Oral Medicine, Diagnosis and Radiology, Desh Bhagat Dental College and Hospital, Muktsar, Punjab, India
2 Department of Oral Medicine, Diagnosis and Radiology, Dayananda Sagar College of Dental Sciences, Bangalore, Karnataka, India
3 Department of Oral Medicine, Diagnosis and Radiology, KLE Society's Dental College, Bangalore, Karnataka, India
|Date of Submission||21-Jul-2014|
|Date of Acceptance||28-Feb-2015|
|Date of Web Publication||22-Apr-2015|
Kumra Dental Clinic, Railway Road, Zira, District Ferozepur - 142 047, Punjab
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Pleomorphic adenoma, also called benign mixed tumor, is the most common tumor of the salivary glands. Usually they are found as solitary, unilateral, firm and mobile, painless, slow growing masses. Only 10% of them occur in the minor salivary glands and 90% of them occur in the parotid gland. The incidence of parotid tumor is about 2.4 in 100000/year of all neoplasia of head and neck region, the right side being commonly involved and seen more often in males. Management involves surgical resection by superficial or total parotidectomy. This case report illustrates clinical features, imaging characteristics and histopathological features in a case of pleomorphic adenoma.
Keywords: Benign mixed tumor, CT scan, FNAC, pleomorphic adenoma, ultrasound
|How to cite this article:|
Dhir P, David CM, Dhaduti KG. Pleomorphic adenoma of the parotid gland with cystic degeneration: A rare case report. J Indian Acad Oral Med Radiol 2014;26:450-3
|How to cite this URL:|
Dhir P, David CM, Dhaduti KG. Pleomorphic adenoma of the parotid gland with cystic degeneration: A rare case report. J Indian Acad Oral Med Radiol [serial online] 2014 [cited 2018 Oct 22];26:450-3. Available from: http://www.jiaomr.in/text.asp?2014/26/4/450/155661
| Introduction|| |
Salivary gland tumors are rare, comprising less than 3% of all neoplasms of the head and neck region and are known by their complex microscopic features. Also called as benign mixed tumor, it accounts for 60% of all benign salivary gland tumors.  It is followed by Warthin's tumor, which accounts for about 4-14% of all parotid tumors. Approximately 90% of parotid tumors occur in the superficial lobe while the remaining 10% occur in the deep lobe, lying under the facial nerve.  Histologically parotid glands can give rise to a wide variety of benign and malignant neoplasms because of their mixed array of cells and tissues. An incomplete connective tissue pseudo-capsule envelopes the lesion with isolated nodules of tumor lying within and outside it, due to which there is a possibility of rupture of the capsule at surgery and following which recurrence may occur.  The most widely accepted surgical treatment for parotid tumors is conservative parotidectomy.  We report a case of benign pleomorphic adenoma of the parotid gland in a 35-year-old male patient.
| Case Report|| |
A 35-year-old male patient reported to the department with a chief complaint of an asymptomatic swelling on the left side of the face since 6 months which was gradual in onset and had increased to the present size. There was no history of pain or trauma and his past dental and medical history was noncontributory. There was no symptom suggestive of facial nerve involvement.
The clinical examination revealed a diffuse swelling on the left lower 1/3 rd of the face measuring about 2 × 1.5 cm in size extending anteroposteriorly from the angle of the mandible to an area 4 cm posterior to the corner of the mouth and superoinferiorly extending from a point 1 cm below lobule of the ear to 0.5 cm below the lower border of the mandible [Figure 1]a and b. The skin over the swelling appeared to be normal; there was no discharge or any other secondary findings. On palpation, the swelling was nodular, non-tender, firm in consistency, non-fluctuant, compressible, non-pulsatile and was not fixed to the surrounding structures. The temperature over the swelling was normal. On intraoral examination of the parotid papilla, a thin, watery flow of saliva was present.
|Figure 1: Image of left lateral view of face showing (a) Anteroposterior and (b) Superoinferior extension of the swelling|
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The radiographic investigations such as ultrasound and computed tomography (CT) scan were done to assess the extent of the lesion. In ultrasound, the left parotid gland revealed a hypoechoic well-defined lesion at its inferior pole posteriorly measuring approximately 1.0 × 3.8 cms. It exhibited very minimal internal debris. No evidence of any calcification was seen [Figure 2]. The plain and contrast CT scan were performed which showed a focal hypodense lesion with enhancing wall measuring 17 × 15 mm in the lower aspect of the superficial lobe of the left parotid gland and few mildly enlarged submandibular and upper cervical group of lymph nodes bilaterally, largest one measuring 18 × 11 mm revealing an impression of a bilateral mildly bulky parotid gland- suggestive of sialadenitis/parotitis with a small abscess in the superficial lobe of the left parotid gland and multiple mildly enlarged cervical group of lymph nodes bilaterally [Figure 3]a and b. Fine needle aspiration cytology (FNAC) was performed as an adjunct to diagnosis prior to definitive surgical treatment. The smear showed a mixture of spindle cells and round cells i.e., myoepithelial and ductal cells in clusters as well as individually in a fibromyxoid background, which was suggestive of a benign salivary gland neoplasm (pleomorphic adenoma) [Figure 4]. Based on the history given by the patient and clinical examination a provisional diagnosis of benign salivary gland neoplasm of the left side parotid gland was given for which differential diagnosis of pleomorphic adenoma and Warthin's tumor was given. The superficial parotidectomy of left parotid gland region was performed under general anesthesia. The excised superficial lobe of the parotid gland showed normal salivary tissue with a focus showing a well-circumscribed cystic lesion composed of myoepithelial cells arranged in cords, acinar pattern dispersed in areas of myxoid stroma and the lymph node showed reactive changes. The final histopathology report confirmed the diagnosis of benign pleomorphic adenoma of the left side of parotid gland [Figure 5]a and b. No complications were observed after a 6-month follow-up.
|Figure 2: US image revealing a well-defi ned cyst at its inferior pole posteriorly in the left parotid gland|
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|Figure 3: (a) Coronal and (b) Axial CT section showing the lesion involving the left parotid gland|
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|Figure 4: Hematoxylin and eosin-stained section showing clusters of round and spindle cells in a fibromyxoid background|
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|Figure 5: Hematoxylin and eosin-stained section in (a) Lower magnification showing epithelial cells in sheets and cords with chondro myxoid stroma, and (b) Higher magnifi cation showing myoepithelial cells arranged in cords, acinar pattern dispersed in areas of myxoid stroma|
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| Discussion|| |
Pleomorphic adenoma is the most common benign salivary gland tumor with parotid gland being the most common affected site. Everson and Cawson found that 73% of salivary gland tumors occurred in the parotid gland and that 63.3% of these were pleomorphic adenomas. They found an age range of 13-87 years with an average of 46 years and a slight female propensity.  The typical parotid tumor is found below the lobule of the ear and overlying the angle of the mandible. On gross finding, pleomorphic adenoma is a single, firm, mobile, well-circumscribed mass. They are irregularly shaped and have a bosselated surface. , Symptoms and signs depend on the location. When the tumor occurs in the parotid gland, symptoms related to the facial nerve are infrequently seen; in large neglected tumors, however, facial nerve weakness is likely to arise as the result of malignant change. The incidence of malignant transformation ranges from 1.9 to 23.3%. 
The term "Pleomorphic" refers to both histogenesis and histology of the tumor. The tumor has three components: An epithelial cell component, myoepithelial cell component and mesenchymal component. The identification of these three components is essential for the recognition of pleomorphic adenoma.  Histologically, pleomorphic adenoma presents with a variable pattern of epithelium in a loosely fibrous stroma which may be myxoid, chondroid, or mucoid. The myoepithelial cells are often polygonal with a pale eosinophilic cytoplasm. These cells are typical and diagnostic in small biopsies. In most instances, the diagnosis of pleomorphic adenoma is a straight forward microscopic identification. 
Different imaging modalities such as ultrasound (US), FNAC, magnetic resonance imaging (MRI) and CT can be used to assess salivary gland disease. The choice of imaging modality depends on the local protocol, clinical features and the site of suspected pathology. However, only surgery can give histological certainty of tumor nature and prevents long-term malignant degeneration or lump infection or size-dependent facial nerve damage. 
Ultrasound is the investigation of choice for major salivary gland disease since it is quick and economical and a thorough assessment of the gland can be done without the use of ionizing radiation. It can also be used for imaging guidance for FNAC and core biopsy as was done in the present case. 
Today, multislice CT is one of the primary imaging modalities used to assess tumors of the salivary glands as was done in the reported case. It allows the detection of lesions and assessment of their extension and characteristics as well as their relationships to nearby structures.  The typical CT appearance of parotid pleomorphic adenoma has been reported as that of a smoothly marginated or lobulated small spherical tumor. Pleomorphic adenomas have also been described as not significantly enhancing, with larger masses often having a nonhomogeneous appearance characterized by low-attenuation central foci of necrosis, old hemorrhage, and cystic change.  Pleomorphic adenomas are hypoechoic, well-defined, lobulated tumors with posterior acoustic enhancement and may contain calcifications in US imaging. , Fine needle aspiration cytology can be useful in choosing the right surgical approach as was done in the present case. 
The differential diagnosis for this case include benign salivary gland tumors such as pleomorphic adenoma and Warthin's tumor as both these tumors present with similar clinical presentation but diagnosis would be confirmed after histopathology as done in the reported case. It has been said that pleomorphic adenoma accounts for 55% and Warthin's tumor accounts for 15% of all tumors in parotid glands. The malignant salivary gland tumors such as mucoepidermoid carcinoma could be ruled out in the present case as the patient did not present with signs of facial nerve involvement.
The reported case had been associated with cystic degeneration and very few cases have been reported with cystic degeneration. A cyst can result from degeneration, necrosis or hemorrhage within the tumor.  Nishimura et al. reported two cases of pleomorphic adenoma of the parotid gland with cystic degeneration.  Maji et al. described a case of pleomorphic adenoma involving the minor salivary glands of the upper lip with extensive cystic degeneration.  Park et al. described a case of tender, cystic mass on the right cheek. The total surgical excision was done under an impression of an epidermal cyst but histopathological findings revealed pleomorphic adenoma with cystic degeneration.  Chen et al. described two unusual cases of pleomorphic adenoma associated with extensive necrosis.  Sudheendra et al. reported three cases of pleomorphic adenoma of the minor salivary glands with cystic changes.  The reported case presented as a diagnostic dilemma, as in the ultrasound it presented as a cystic lesion and in the CT scan it presented as an abscess which was suggestive of sialadenitis but histopathology confirmed the final diagnosis of pleomorphic adenoma.
Treatment of pleomorphic adenoma is surgical resection. Surgical resection of the tumor can be done by enucleation, superficial total parotidectomy. Recurrence is least in total parotidectomy compared to enucleation and superficial parotidectomy. Recurrence of pleomorphic adenoma following surgery was recorded in 0.5-10%, in some reports rising to 48% as pleomorphic adenoma do not have a true capsule.  Following parotid gland surgery, many of the difficulties and complications are due to the relationship of the facial nerve to the parotid gland. Most commonly there is chance of transient facial paresis, Frey's syndrome. In the present case, 6-month follow-up after total parotidectomy, no complications or recurrences are observed.
| Conclusion|| |
In summary, pleomorphic adenoma is the most common tumour to arise in the parotid gland. Diagnosis becomes difficult when such a tumor undergoes cystic degeneration and presents with unusual findings. This can lead to erroneous decisions concerning treatment. To our knowledge, the reported case represents a rare case of pleomorphic adenoma with cystic degeneration and illustrates the need for detailed history, diagnostic imaging and adequate tissue sampling to rule out malignancy and the other cystic lesions associated with salivary glands. Proper diagnosis and careful surgical resection with preservation of the facial nerve helps in better prognosis with least chances of their recurrence.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]