What is a pleomorphic adenoma (benign salivary gland tumor)?

From the Guidelines

Pleomorphic adenoma is a benign salivary gland tumor that requires complete surgical excision to prevent potential malignant transformation and recurrence, with treatment typically involving superficial parotidectomy with facial nerve preservation for parotid tumors, as supported by recent guidelines 1.

Key Characteristics

• Pleomorphic adenoma is the most common type of benign salivary gland tumor, typically occurring in the parotid gland
• It presents as a slow-growing, painless, firm mass that can affect people of any age but is most common in adults between 30-60 years old
• The tumor is characterized by its mixed composition of epithelial and mesenchymal elements, which gives it the name "pleomorphic" meaning many forms

Treatment and Prognosis

• Treatment involves complete surgical excision, usually through superficial parotidectomy with facial nerve preservation for parotid tumors, or local excision for those in minor salivary glands
• While benign, pleomorphic adenomas require removal because they can continue to grow, causing cosmetic concerns and pressure symptoms, and approximately 5-10% may undergo malignant transformation if left untreated for many years
• Recurrence is possible if removal is incomplete, which is why wide surgical margins are preferred, as seen in studies where close surgical margins (≤ 5 mm) still resulted in excellent disease control in low-grade parotid cancers 1
• Patients typically have an excellent prognosis following complete removal, with most achieving full recovery without complications, and a 5-year disease-free survival rate of 90.6% has been observed in patients with low- or intermediate-grade parotid cancers managed with surgery alone 1

From the Research

Definition and Characteristics of Pleomorphic Adenoma

• Pleomorphic adenoma (PA) is the most common neoplasm of the major salivary glands 2.
• It is a benign mixed tumor, which has three components: an epithelial component, a myoepithelial cell component, and a mesenchymal component 3.
• PA generally presents as a slowly progressing painless swelling, which is well-delineated, nonsymptomatic, and not involving the facial nerve 3.
• The diagnostic marker pleomorphic adenoma gene 1 (PLAG1) is frequently employed since it is specific for pleomorphic adenoma 3.

Clinical Features and Diagnosis

• PA can occur in the parotid gland, submandibular gland, and minor salivary glands 2, 3, 4, 5, 6.
• The mean age of PA occurrence is around 44-57 years with a female predilection 3, 5.
• Fine-needle aspiration biopsy, ultrasonography, and computed tomography scan can be used for diagnosis 3.
• Calponin, cluster of differentiation 9 (CD9), glial fibrillary acidic protein (GFAP), and other markers exhibit positive reactions in pleomorphic adenomas 3.

Treatment and Outcomes

• Surgical excision with facial nerve preservation is the optimal treatment for PA, resulting in local control rates of 95% or higher 4, 5, 6.
• Radiotherapy can be used to obtain local control in patients with positive margins, unresectable tumors, and multifocal recurrences after prior resection 4.
• Complete excision of the tumor is the definitive treatment, as enucleation can result in recurrence 5.
• The 5-year survival rate for patients with carcinoma ex pleomorphic adenoma (CXPA) is around 73.6-87.5% 2.