Rare Parotid Gland Diseases.

The differential diagnosis for "rare" parotid gland diseases is broad and encompasses infectious, neoplastic, autoimmune, metabolic, and iatrogenic etiologies. The body of knowledge of parotid gland diseases has grown owing to advances in imaging and pathologic analysis and molecular technology. This article reviews rare parotid diseases, discussing the respective disease's clinical presentation, diagnosis, imaging, pathogenesis, treatment, and prognosis.