Pleomorphic Adenoma - A Case Report on an Abnormal Mass

Abstract

Rationale:

Pleomorphic adenoma (PA) is the most prevalent salivary gland tumour, accounting for 60%–80% of all benign salivary gland tumours, and frequently affects the parotid gland. Their epithelial and connective tissue origins can explain the ‘pleomorphic’ nature of tumours. This tumour is most common in women between 30 and 50 years.

Patient Concerns:

A 45-year-old female came with the chief complaint of a slow-growing, painless swelling on the left side of her face that had been present for 25 years.

Diagnosis:

PA of the parotid gland was diagnosed using computed tomography and fine-needle aspiration cytology. PA is a slowly progressing, asymptomatic swelling that rarely exceeds 6 cm in its greatest dimension; in our case, it was 13 cm × 10 cm and weighed 5 kg.

Treatment:

The ideal management is the surgical removal of the tumour mass, which was done under general anaesthesia. Early diagnosis and treatment planning was critical. Complete removal of the tumour without remnants is crucial to prevent a recurrence. Total parotidectomy was done in this case.

Outcomes:

There was no evidence of recurrence after comprehensive local surgical resection of the tumour during the follow-up period.

Take-away Lessons:

This case report is significant as it sheds light on the successful treatment approach for a large pleomorphic adenoma. It can provide valuable insights into the management of similar cases, potentially leading to improved patient outcomes and guiding future treatment strategies.

INTRODUCTION

Salivary gland tumours are rare as it makes up only 3% of head-and-neck cancers and about 2%–6.5% of all head-and-neck neoplasms.[1] Since it makes up between 50% and 74% of all parotid tumours, pleomorphic adenoma (PA) is regarded as the most prevalent benign salivary gland neoplasm.[2] It had previously been referred to as a mixed tumour, enclavoma, branchioma, endothelioma, endochroma and so on. PA is found mostly in the parotid glands (85%), minor salivary glands (10%) and submandibular glands (5%). PA mainly involves the lower pole of the superficial lobe of the parotid gland and only 10% of cases arise in the deep lobe.[3]

PA affects people in their fourth, fifth and sixth decades of life and affects women (60%) more frequently than men (40%).[4,5] PAs typically start as distinct swellings that slowly enlarge and are asymptomatic. In the literature, giant PA of the parotid is described as a rare tumour, most of them being reported before the 1980s. It usually manifests as a slow–progressing, asymptomatic, parotid gland swelling without facial nerve involvement. They are best treated by a wide local excision with good safety margins and follow-up for at least 3–4 years.[6]

CASE REPORT

A 45-year-old female patient presented with a major complaint of a slow-growing, painless swelling on the left side of her face that had been present for 25 years. The swelling was initially small in size and has gradually grown to its current size over time. Past medical and surgical history was irrelevant. An extra-oral clinical assessment found significant facial asymmetry. On the left side of the face, a well-defined, ovoid, multi-lobular swelling of 13 cm × 10 cm was observed.

The swelling had the superoinferior extent 2 cm below the ala-tragal line to the clavicular region and the anteroposterior extent from the midline of the neck to the anterior border of the trapezius. The left ear lobule was everted giving one of the typical signs. Loss of wrinkling of the skin and engorged veins was also seen on the surface of the swelling [Figure 1]. The swelling was firm in consistency, non-tender and slightly warm on palpation. The intraoral examination discovered no notable findings. The growth was concealed by intact healthy mucosa. On bimanual palpation, the mass could be felt between the buccal mucosa and the skin, but it was not attached to any deeper tissues. Milking of the gland showed lesser saliva secretion. The mouth opening was satisfactory. The opening of Stenson’s duct was present in the normal position. Signs of Bell’s palsy were noted on conducting facial nerve examination. A left parotid gland benign tumour was proposed as a preliminary diagnosis. The tumour’s size of 13 cm × 10 cm was measured and recorded [Figure 2].

Figure 1.

Photograph of patient, pre-operation

Figure 2.

Measurement of the tumour size

Computed tomography (CT) showed a large mass in the left neck. It was predominantly solid and showed uneven enhancement [Figure 3]. A strong enhancement focus of 13 cm × 10 cm was noted on its inferior and medial sides. The lesion did not involve the sternocleidomastoid muscle, carotid artery, left submandibular salivary gland or mandible. The lesion had an arterial supply from the facial artery and venous drainage through the internal jugular vein. Fine-needle aspiration cytology (FNAC) was performed under local anaesthesia (LA), which showed admixed epithelial, myoepithelial and mesenchymal tissue elements. Since incisional biopsy of PA may predispose to recurrence, it is contraindicated in our case.

Figure 3.

Computed tomography - showing tumour pre-operation

The patient was hospitalised and the procedure was well explained to her. After obtaining informed consent from the patient, under general anaesthesia and all aseptic precautions, the usual painting and draping were carried out and the incision line was marked. A modified skin incision was placed. Soft tissues were carefully dissected in a clear plane to prevent injury to the adjacent vital structures [Figures 4-6]. After identifying the anterior greater auricular nerve in the preauricular area, it was sacrificed. Further care was taken for the identification of the main branch of the facial nerve and the tumour along with the gland was excised completely along with some normal skin [Figure 7]. The resected tumour which measured approximately 13 cm × 10 cm with an irregular surface was sent for a final histopathological examination. A nasogastric tube was used to feed the patient for three days. Antibiotics and local Betadine were administered as part of the post-operative treatment.

Figure 4.

Patient painting and surgery preparation

Figure 6.

Gross specimen of the resected tumour mass

Figure 7.

Tumour mass measuring 13 cm × 10 cm

Figure 5.

Blunt dissection with the exposed tumour mass

The patient was then discharged after three days. Histological examination showed it to be a PA of her left parotid gland. Layers of epithelial cells and well-encapsulated cell masses of islets and rounded myoepithelial cells were evident, along with a myxomatous background and ductal architecture [Figure 8]. The postoperative follow-up was uncomplicated. The patient has been followed up annually, has shown no signs of recurrence and has had no adverse or unanticipated events [Figure 9].

Figure 8.

Histopathological image of pleomorphic adenoma (40X magnification)

Figure 9.

Post-operative facial view

DISCUSSION

The term ‘PA’ was first coined by Dr. Willis. PA is the most prevalent benign salivary gland neoplasm and accounts for approximately 50%–74% of all parotid tumours. Although PAs can have a wide range of morphologies, they are not true ‘mixed tumours’ formed from more than one germ layer; instead, they are entirely epithelial in origin, containing ductal and pluripotent myoepithelial cells. PAs have a global yearly incidence rate of 2.4–3.05 per 100,000 people. The exact aetiology of PA is unknown, although its prevalence has increased in the previous 15–20 years in response to radiation exposure. According to one study, the oncogenic simian virus 40 may be involved in the development or progression of PA. Previous radiation to the head and neck is another risk factor for the formation of these tumours.[7]

Clinically, the PA presents as an irregular, rubbery, lobulated and slow-growing mass with no associated pain or discomfort. The presenting complaint is often connected to an unpleasant or unaesthetic facial look, which if ignored might result in patients reporting large lesions. Our patient presented with this typical clinical feature along with the facial nerve impairment and gravity traction, which leads the tumour mass in large PA to drop away to the neck region. When resected, most of these tumours are 2–6 cm in size. Large tumours frequently form a single, irregularly nodular mass that stretches the surrounding skin or mucosa, and their weight can range from a few grams to more than 8 kg; the resected tumour in our case weighed 5 kg. It is puzzling to note the time taken by the patient to seek medical attention was nearly 25 years. The rationale for the late presentation was the negligence of the patient in the initial periods since there was no pain associated with the tumour. The constant enlarging swelling gave them the fear of surgery and to seek folk medicine. Immunohistochemistry can help distinguish pleomorphic salivary adenoma from other tumours and identify different cell types. Approximately 70% of PAs have cytogenetic abnormalities. The two particular gene translocations associated with pleomorphic salivary adenoma are HMGA2 and PLAG1.[8]

With the introduction of cross-sectional imaging modalities such as CT and magnetic resonance imaging (MRI), diagnostic imaging of salivary glands has been transformed; hence, these two modalities can be considered as a gold standard of PA. It helps in determining the size, extent of lesions, and bone involvement. In our case, we preferred to use CT over MRI to see the exact bone involvement of the lesion. The accuracy of FNAC in diagnosing PA has been reported to range between 89.5% and 96.2%. As a result, we employed this modality to accurately diagnose PA when also distinguishing between benign and malignant tumours to choose the best treatment strategy. The cytological diagnosis of PA is easy. It is very common to find bland epithelial cells in irregular aggregates, as well as metachromatic fragments of fibrillary chondromyxoid stroma with spindle cells. Malignant transformation in PAs occurs at a rate ranging from 1.9% to 23.3%. Tumours with a long evolution period, recurrences, advanced age of the patient and location in a major salivary gland have a higher risk. Although our patient presented with certain characteristics of malignant risk, further clinical and microscopical investigations reveal no such evidence luckily.[9]

Our case is treated by the total parotidectomy with a sacrifice of greater auricular nerve and facial nerve of the involved side due to its huge size and invasion of those structures.[10] The main reason for such invasive treatment is to ensure the complete removal, thereby preventing the recurrence. The recurrence rate ranges from 2%–5% after surgical resection. Our patient has been followed closely for two years with no signs of recurrence.

CONCLUSION

PA of the cheek region is an uncommon tumour; hence, diagnosing it requires a high level of suspicion. Treatment is determined by the extent of the tumour, and in our instance, we had done total parotidectomy. Patients should be monitored for an extended period of time due to the likelihood of late recurrences. Even if the probability of malignant transformation of the PA is low, it is critical to treat the patient as soon as possible to limit the risk of malignancy. In our case, even though there is no malignant change, late intervention resulted in the sacrifice of certain key tissues and harm to the patient.

Declaration of patient’s consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.