Hyalinizing clear cell carcinoma of salivary gland.

We describe 11 patients with a distinctive salivary gland neoplasm. Most of the patients were adult women who presented with a painless mass. Nine tumors arose in minor salivary glands of the oral cavity (82%). Microscopically, they were characterized by the formation of trabeculae, cords, islands, and/or nests of monomorphic clear cells that were glycogen rich and mucin negative and were surrounded by hyalinized bands with foci of myxohyaline stroma. Cells with eosinophilic and granular cytoplasm were also noted. Both cell types showed minimal nuclear pleomorphism and a very low mitotic index. The neoplasms all had infiltrative borders. Immunohistochemically, the tumor cells expressed cytokeratins and epithelial membrane antigen, but not S-100 protein and smooth muscle actin. Ultrastructurally, the tumor cells contained abundant glycogen, desmosomes, peripheral tonofilaments, and prominent interdigitating microvilli without actin myofilaments or dense bodies. These immunohistochemical and ultrastructural findings provide evidence of epithelial differentiation without myoepithelial differentiation. For these tumors, we propose the name, hyalinizing clear cell carcinoma (HCCC). These are low-grade malignant neoplasms. Two patients had ipsilateral cervical lymph node metastases at presentation, but with surgical excision and either preoperative or post-operative radiotherapy in three cases, eight of 10 patients with clinical follow-up are alive and well without evidence of recurrence. The mean clinical follow-up is 3.6 years, with a range of 6 months to 11 years. One patient died as a result of surgery, another died of unrelated causes, and one patient was lost to follow-up.