A Case of Faster Growing Warthin’s Tumour in Primary Care

Around 3% of all head and neck malignancies are salivary cancers, most of these are in the parotid glands.³ Approximately 80% of salivary gland tumors occur in the parotid gland and approximately 75- 80% of these are benign. Most benign parotid tumors are slow growing, painless masses often in the tail of the parotid gland. The most common salivary gland tumor is the pleomorphic adenoma which comprises about half of all tumors and 65% of parotid gland tumors. It is also the most common minor gland lesion representing 40% of intraoral tumors and about 50% of those on the palate. Warthin’s tumor is the second most common benign lesion.¹ The most common malignant tumor is mucoepidermoid carcinoma, followed by acinic cell carcinoma and adenoid cystic carcinoma.⁴

Warthin’s tumor accounts for 5-20% of all salivary gland tumors.^5,6 It is slow growing with average 8% growth per year, with an approximate doubling time of 9 years, but can have a wide range of growth rates. It involves almost exclusively the parotid gland, especially the inferior part and peri parotid lymph nodes and present bilaterally in 5-17% of the patients. It is more frequently reported between 40 to 70 years of age with an average age at diagnosis of 62 years. ^5,6 Although it is more common in males but due to increasing rates of smoking in females, the sex ratio has shown tendency of equalization in last few decades. The association between smoking and Warthin’s tumor has been reported since 1980’s with 8-fold increase in smokers as compared to non-smokers. This is hypothesized to be caused by the retrograde flow of substances in tobacco smoke into salivary ducts or by excretion of substances from smoke into the ducts.^1,7 The other risk factors hypothesized include exposure to ionizing radiations (in atomic bomb survivors) and autoimmune diseases (e.g., thyroiditis).^1,7 It usually presents as a slow growing fluctuant mass in lower portion of parotid gland. Magnetic resonance imaging (MRI) is the best and most accurate imaging method and provides detailed description about extension of the mass, but it is more expensive and time consuming. CT scan is more accessible method. Ultrasound is important in guiding FNAB, allows the radiologist to evaluate solid and cystic component and facilitates to sample the solid tumor component.¹   Histopathology remains the main stay of diagnosis and FNAB of parotid gland has high specificity (98%), moderate sensitivity (78%) and excellent accuracy (96%) in differentiating between benign and malignant lesions. On histopathology, Warthin’s tumor is composed of varying proportions of papillary- cystic structures lined by oncocytic epithelial cells and a lymphoid stroma with germinal centres. The epithelial component is formed of inner columnar and outer cuboidal cells. Some foci of mucous, ciliated, sebaceous, and squamous cells can be present in Warthin’s tumors. The recommended treatment of Warthin’s tumor is surgical removal which can be easily performed due to the superficial location of the tumor. Some surgeons prefer local resection with surrounding tissue; others choose superficial parotidectomy in order to avoid the rupture of tumor capsule.^{1, 7} The risk of malignant transformation is very rare, and recurrence is very uncommon, however, multifocality and bilaterality is frequent, especially in heavy smokers.¹