A 52-year-old man from Delhi presents with a 6-month history of a painless, slow-growing swelling in the right parotid region. On examination, the mass is firm, mobile, and approximately 3 cm in diameter. Intraoral examination reveals no mucosal involvement. Fine-needle aspiration cytology (FNAC) shows epithelial cells arranged in sheets with occasional mucoid material. What is the most likely diagnosis?

## Diagnosis: Pleomorphic Adenoma **Key Point:** Pleomorphic adenoma is the most common benign salivary gland tumor, accounting for 60–70% of parotid tumors and 40–50% of all salivary gland neoplasms. ### Clinical Features - **Presentation:** Painless, slow-growing mass over months to years - **Location:** Parotid gland (80% of cases); can occur in submandibular and minor salivary glands - **Characteristics:** Firm, mobile, well-defined, no facial nerve involvement (unless malignant transformation) - **Age:** Typically 40–60 years ### FNAC Findings | Feature | Pleomorphic Adenoma | | --- | --- | | Cell arrangement | Epithelial sheets, myoepithelial cells | | Background | Myxoid, chondroid, or hyaline material | | Mucoid material | Present (characteristic) | | Atypia | Absent or minimal | **High-Yield:** The presence of **epithelial cells with mucoid/myxoid background** on FNAC is pathognomonic for pleomorphic adenoma. ### Management 1. **Imaging:** MRI or CT for extent and facial nerve relationship 2. **Surgery:** Superficial or total parotidectomy with facial nerve preservation (gold standard) 3. **Prognosis:** Excellent if treated; malignant transformation rate ~5% if untreated for >20 years **Clinical Pearl:** Pleomorphic adenoma is also called "mixed tumor" because it contains both epithelial and mesenchymal (myxoid/chondroid) components histologically. **Warning:** Incomplete excision or rupture during surgery increases recurrence risk (up to 45% with enucleation alone); superficial/total parotidectomy is preferred.