Giant Pleomorphic Adenoma of the Parotid Gland: A Case Report

INTRODUCTION

Pleomorphic adenoma comprises 80% of the benign tumors of the parotid, whereas benign tumors are 85% of the total salivary gland tumors. The parotid is the most common site for salivary gland tumors.¹ These tumors grow as a painless slow-growing mass without many symptoms. In the usual scenario, patient comes for resection by the time the tumor is 6 cm.²

PA is a slow-growing tumor with a low risk of turning malignant, and thus some surgeons prefer to delay or not to operate.¹ This is in contrast to traditional management, which emphasizes that “aggressive treatment of primary and recurrent mixed tumors is necessary”³ due to their malignant potential. This paper describes an unusual case of a giant PA arising in the parotid gland. We decided to study the scenario where benign tumors that do not undergo malignant transformation. In this case, we wish to emphasize that though PA carries a low risk of malignant transformation, but cosmetically it may look gruesome when it takes gigantic proportions and thus cause social morbidity. Therefore, it becomes prudent to operate PA.

CASE DESCRIPTION

A 57-year-old male farmer sought medical attention in our institute for a large growth on the right side of the face. The painless swelling had gradually increased in size over a period of approximately 10 years. On conducting clinical examination, we found that the giant, firm, multinodular, irregular, and painless mass measured approximately 27 cm × 17 cm × 10 cm involving the right parotid (Figs 1 and 2). Though the mass was quite large, there were no signs of facial nerve palsy, and the skin that covered the lesion did not present ulcerated areas. Probably the slow growth of the mass resulted in skin stretching without ulceration. The patient had cosmetic complaints only and had no trouble in breathing or otherwise.

The clinical photograph to show an irregular-shaped large swelling to the right side parotid gland, in 27 cm × 17 cm × 10 cm dimensions in a 57-year-old male patient.

CT scan suggested evidence of a heterogeneously enhancing mass lesion to the right parotid gland. The main hypothesis for diagnosis was a benign tumor of the parotid gland, most likely PA (Figs 3 and 4).

Fine needle aspiration cytology suggested PA.

The tumor was excised under general anesthesia. Despite the size of the mass, a clear subplatysmal plane of dissection was found. The tumor was well separated from the floor (Fig. 5). The sternocleidomastoid muscle was thinned out. The facial nerve was located based on the landmarks (Fig. 5). It passed through the tumor and had to be transacted during the removal of the tumor. Skin flaps were raised off the sides of the mass to provide sufficient tissue for neck closure.

Post surgery, the patient had a grade 3 facial palsy (House Brackmann Staging) which progressed to grade 4 palsy one week later (Fig. 6).

Macroscopically, the excised mass measured 27 cm × 17 cm × 10 cm and weighed 2.250 kg. Microscopic sections show fibrocollagenous tissue infiltrated by cellular tumor composed of tubular epithelial structures enveloped with myoepithelial cells in a chondromyxoid stroma. The epithelial cells are columnar to cuboidal. The myoepithelial cells are spindle to polygonal. The lumen of a few of the tubules contains eosinophilic material. No evidence of necrosis, cellular atypia, or frequent mitoses is noted. Histomorphology is suggestive of PA.

DISCUSSION

Pleomorphic adenoma is the most common salivary gland tumor. The main site of occurrence is the parotid gland, affecting patients of any age, mostly between the fifth and sixth decades of life.⁴ Although uncommon, cases of giant pleomorphic adenomas (PAs) have been described, the majority of which involved the parotid gland. The first case of giant PA published in medical literature was reported by Spence,⁵ who described the treatment of a mixed tumor > 1 kg. In 1956, Short and Pullar⁶ published an English language review of massive PAs and a case report of a 2.3 kg adenoma. In 1989, Schultz-Coulon⁷ reviewed 31 cases of giant PAs of the parotid gland. The author found a female predominance (64.5%), with age ranging from 20 to 40 years old.

In most cases, patient ignorance, absence of pain, and fear of treatment delay the treatment and specifically surgery. In our case, it must be considered that the mass was painless, and the patient was ignorant and had a fear of treatment, the reason for the delay.

The incidence of malignant transformation in adenomas ranges from 1.9 to 23.3%.⁸ The risk increases in tumors with long-standing evolution, recurrence, the advanced age of the patient, and location in a major salivary gland.⁹ Some authors postulated that the risk of malignant transformation increases from 1.6% in tumors with less than 5 years of evolution, to 9.5% for those presenting for more than 15 years.¹⁰ The classic clinical history of carcinoma ex-PA is a slow-growing mass for many years, with a recent fast growth phase.

In the Schultz-Coulon⁷ review, 3 of 31 cases of giant adenomas showed areas of malignant transformation. In our case, although the patient presented all the characteristics of an increased risk of malignancy, clinically and histologically there was no such evidence. Neglecting even a benign parotid tumor carries an increasing risk of facial nerve injury when treatment is performed, as in our case where the facial nerve was embedded in the tumor, which had to be transacted intraoperatively. The bony and muscular deformity associated with such tumors is uniformly disfiguring and incapacitating.

Reporting a case of this nature has significance as delayed intervention allows for rapid tumor growth (believed by some to be due to mutated ras genes¹¹), cosmetic issues, social morbidity, and a possible threat to life especially with the presence of tumor pressure over the parapharyngeal space and oropharynx, which could be compounded by infection, thus threatening the airway. The expanding mass could further distort the anatomy thus displacing vital structures and making the dissection more challenging. We advocate early excision of parotid PAs so as to prevent conversion to malignant mass or growing to large proportions causing complications per se or during surgery at the time of removal.

ACKNOWLEDGEMENTS

REFERENCES

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