Benign Parotid Tumor (e.g., Pleomorphic Adenoma): This is the most common type of salivary gland tumor and often presents as a slow-growing, painless swelling in the parotid gland.

Parotitis (Viral or Bacterial): Inflammation of the parotid gland can cause swelling and is often associated with pain, fever, and sometimes pus discharge. Viral parotitis (mumps) is more common in children, while bacterial parotitis can occur at any age.
Sialadenitis (Chronic): Chronic inflammation of the salivary gland can lead to recurrent swelling and pain, often related to stone formation or ductal obstruction.
Sjögren's Syndrome: An autoimmune disorder that can cause swelling of the parotid glands due to inflammation and lymphocytic infiltration, often accompanied by dry eyes and mouth.

Parotid Malignancy (e.g., Mucoepidermoid Carcinoma, Adenocarcinoma): Although less common than benign tumors, malignant tumors of the parotid gland can present similarly and require prompt diagnosis and treatment to improve prognosis.
Lymphoma Involving the Parotid Gland: Both primary and secondary (metastatic) lymphoma can involve the parotid gland, presenting as swelling, and is critical to diagnose due to its implications for treatment and prognosis.

Warthin's Tumor: A rare, benign tumor of the salivary gland that can cause swelling, more commonly found in the parotid gland and often associated with smoking.
Kimura Disease: A rare, chronic inflammatory disorder that can cause swelling of the parotid gland, often accompanied by lymphadenopathy and eosinophilia.
HIV-Associated Parotid Swelling: In patients with HIV, parotid swelling can be due to various conditions, including benign lymphoepithelial cysts or diffuse infiltrative lymphocytosis syndrome (DILS), highlighting the importance of considering the patient's immune status in the differential diagnosis.