[Clinicopathological features of hyalinizing clear cell carcinoma of the salivary glands: an analysis of 65 cases].

Objective: To investigate the clinicopathological features, immunophenotype, and gene rearrangement status of hyalinizing clear cell carcinoma (HCCC) of the salivary glands, in order to better understand this rare tumor and improve its precision diagnosis and treatment. Methods: A total of 65 cases of salivary gland HCCC diagnosed at the Peking University School and Hospital of Stomatology, Beijing, China between January 2001 and May 2024 were collected. Clinical features, pathological characteristics, EWSR1 gene rearrangement, and follow-up data were analyzed. Results: There were 33 males and 32 females. The age of the patients ranged from 22 to 85 years, with a median age of 54.0 (40.0, 63.5) years. 93.8% (61/65) of the tumors occurred in the minor salivary glands, most commonly in the palate. Microscopically, the tumors were mainly composed of clear tumor cells. Squamous differentiation was observed in 66.2% (43/65) of the tumors, and mucinous cells in 36.9% (24/65). The tumor stroma showed delicate fibrous septa or hyalinized sheets between tumor nests. Lymph node metastasis occurred in 12.3% (8/65) of the cases, and high-grade transformation was observed in 6.2% (4/65). Tumor cells were all positive for p40 and p63, while SOX10 was positive in 12.3% (8/65) of them. Myoepithelial markers were negative. EWSR1 gene rearrangement was detected in 96.6% of the tumors. Follow-up data showed a 5-year overall survival rate of 93.8%, a local recurrence rate of 9.2%, and a distant metastasis rate of 4.6%. Conclusions: HCCC predominantly arises in minor salivary glands and generally has a favorable prognosis. However, a small proportion of the cases may show high-grade transformation, lymph node metastasis, local recurrence, or distant metastasis. It thus requires long-term and regular follow-up. Accurate diagnosis should be based on a comprehensive assessment of histopathological features, immunophenotype, and gene fusion status.