A Symptomatic Case of Adenomatous Ductal Proliferation/Hyperplasia with a Large Cystic Lesion.

Adenomatous ductal proliferation/hyperplasia (ADP/H) of the salivary gland, a rare asymptomatic nonneoplastic lesion that histopathologically resembles basal cell adenoma, is typically incidentally identified in resected specimens of other salivary diseases such as tumors and chronic sialadenitis. A 70-year-old male was referred to our hospital with a 9-month history of continuous swelling in the left parotid region. A physical examination revealed a soft mass in the left parotid gland, which was identified as a cystic mass by computed tomography. A parotid tumor with cystic components was suspected, and partial parotidectomy was performed under general anesthesia. The histopathological findings were consistent with the diagnosis of ADP/H of the salivary gland. This case report emphasizes the necessity for a proper diagnosis of ADP/H of the salivary gland. Further large case series are required for a modification of the definition of ADP/H for its correct diagnosis.