Tumor-associated lymphoid proliferation in the parotid gland. A potential diagnostic pitfall.

A substantial proportion of neoplastic and nonneoplastic parotid diseases have a prominent lymphoid component. The lymphoid element in lesions such as papillary cystadenoma lymphomatosum, sebaceous lymphadenoma, and lymphoepithelial carcinoma are readily recognized as a required diagnostic element. However, when other types of benign and malignant salivary gland neoplasms demonstrate tumor-associated lymphoid proliferation, the tumor may be either misclassified or misinterpreted as metastatic disease. Examples of primary benign and malignant parotid neoplasms exhibiting tumor-associated lymphoid proliferation are documented and illustrated. Other parotid lesions that may have a lymphoid element include sialadenitis, cysts with associated lymphoid tissue, parenchymal neoplasms with an expected lymphoid component or those that arise within an intraparotid lymph node, autoimmune disease, malignant lymphoma, and metastatic disease. An approach to recognition and separation of these entities is discussed.