Answer: Warthin’s Tumor

Histology: On cut section (not shown), turbid fluid and tenacious mucoid material oozed from multiple cysts. At the light microscopic level, discrete lymphoid nodules, often containing reactive germinal centers, are lined by a bilayer of epithelial cells having abundant granular cytoplasm (i.e. oncocytes). Together, these two components form papillary structures that project into cystic spaces.

Discussion: Warthin’s tumor is almost exclusively encountered in the parotid gland. It is more likely to be multifocal and bilateral than any other salivary gland tumor. Smoking has been established as an important risk factor, and the incidence of Warthins’s tumor mirrors the smoking trends of a given population. These are cystic tumors that, if ruptured, can elicit fibrosis with pain and fixation to surrounding structures. Accordingly, these benign tumors can sometimes believed to be malignant based on the clinical presentation.

The microscopic features of Warthin’s tumor are so characteristic that this tumor tends to be easily recognized at the microscopic level. It should be noted that the proportion of lymphoid tissue to oncocytes can vary widely from tumor to tumor and even within the same tumor. Warthin’s tumors that lack a prominent lymphoid component are generally referred to as stroma poor and should not be confused with an oncocytoma. Another tumor that shows some morphologic overlap with Warthin’s tumor is the papillary cystadenoma. Unlike Warthin’s tumor, the papillary cystadenoma tends to arise from the minor salivary glands (not the parotid) and it lacks an organized lymphoid compartment.