Clear Cell Carcinoma Arising from Pleomorphic Adenoma of a Minor Salivary Gland: Report of a Case with Fine Needle Aspiration, Histologic and Immunohistochemical Findings

Background: Malignant changes in pleomorphic adenoma (PA) of the salivary gland (carcinoma ex pleomorphic adenoma) are not common. Clear cell carcinoma is a rare form of salivary gland tumor and involves mostly minor salivary glands, especially those of the palate. Only 3 cases of clear cell carcinoma arising in PA have been reported, 2 in submandibular glands and 1 in a minor salivary gland of the palate.

Case: A 53-year-old man presented with an enlarged mass on the left side of the palate. He had a history of palate mass about 30 years earlier; it was excised and reported as PA. Since then the tumor had recurred twice in the same place; it had been excised and was diagnosed as PA again. A few years later the mass showed rapid growth over a few months. Fine needle aspiration of the mass showed epithelial clusters with bland nuclear features and myxohyaline material typical of PA. Also noted were large and small papillary, trabecular and well-circumscribed clusters of neoplastic cells with a moderate amount offoamy, vacuolated cytoplasm with distinct borders. Glandlike and acinar structures with hyaline globule material resembling cannonballs were also noted. The cytology was suspicious for malignancy. Incisional biopsy was reported as PA. Due to the suspicion of malignancy, the whole mass was excised up to the floor of the orbit. The final diagnosis was clear cell carcinoma expleomorphic adenoma.

Conclusion: Due to nonspecific cytologic findings in clear cell carcinoma and a mixture of elements of PA in this case, we did not consider clear cell carcinoma as the malignant component.