• The parotid gland normally contains several intraparotid lymph nodes. Intraparotid and periparotid lymph nodes may contain ectopic salivary gland tissue.
• Warthin tumor arises within intraparotid (and occasionally periparotid) lymph nodes, apparently within ectopic glandular tissue. The lymphoid component of Warthin tumor derives from the lymphoid tissue of these nodes. This lymphoid tissue is normal or reactive, rather than neoplastic.
• The epithelial/glandular component of Warthin tumor is neoplastic. This component may occupy all or only part of the node in which the tumor arises.
• Warthin tumor is frequently multifocal. Consequently, parotid glands with grossly evident Warthin tumors often contain additional, clinically inapparent Warthin tumors. In some cases of Warthin tumor resected by unilateral parotidectomy, patients develop Warthin tumors in the contralateral parotid gland several years later.
• Warthin tumor occurs most commonly occur in men over 50 years of age. In terms of its natural progression when the lesion remains untreated, some cases (especially large tumors) undergo infarction. Rare cases of poorly differentiated carcinoma arising within Warthin tumors have been reported.
