Pleomorphic adenoma of the parotid gland 1985-2010: A Danish nationwide study of incidence, recurrence rate, and malignant transformation.

Background: Pleomorphic adenoma is the most frequent salivary gland tumor and is known for its tendency to recur and for its ability to transform to carcinoma ex pleomorphic adenoma (Ca-ex-PA). Along with pleomorphic adenoma demographics, we present the first nationwide study with long-term follow-up on these topics.

Methods: The Danish Pathology Data Bank was searched for parotid pleomorphic adenoma and Ca-ex-PA in the period 1985 to 2010 and all pathology descriptions were reviewed. Ca-ex-PA specimens were reviewed by a pathologist.

Results: A total of 5.497 patients were identified and 2.86% had at least one recurrence. An incidence of 4.29/100,000/year was found. The rate of malignant transformation in recurrent pleomorphic adenoma was 3.3%.

Conclusion: We report an up-to-date assessment of the epidemiology of pleomorphic adenoma. We found an increasing incidence and low recurrence rate compared with previous studies. The risk of Ca-ex-PA for patients with recurrent pleomorphic adenoma was low compared to the literature. © 2015 Wiley Periodicals, Inc. Head Neck 38: E1364-E1369, 2016.