Unusual differentiation of a combination tumor of the parotid gland. A case report.

A 67-year-old female patient developed a slowly growing swelling in the region of the left mandibular angle. This swelling was tender on pressure. Clinical examinations revealed an immobile, circumscribed, palpable node. Sonography showed an inhomogeneous space-occupying mass with a predominantly poor echo in the cranial and dorsal parts of the parotid gland. Intraoperatively the lesion presented as a smooth-bordered, round, capsulated tumor, which was excised "in toto". The postoperative course was uneventful. Histologic examination revealed a salivary gland tumor consisting of two components. Glandular structures corresponding to a Warthin tumor were seen in the center, whereas differentiation in the periphery of the tumor was that of a sebaceous lymphadenoma. Metaplastic sebaceous glands within salivary glands have been occasionally described, but true sebaceous lymphadenomas of the salivary glands are a rarity. A rare variant of Warthin's tumor is its metaplastic type, in which extensive metaplasia of the squamous epithelium is observed. The morphologic parallels as well as the differences seen in our case are described. We believe that it does not meet the criteria of a metaplastic Warthin tumor and have therefore diagnosed a combination tumor of the parotid gland, which is composed of a Warthin tumor component and a sebaceous lymphadenoma component.