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?