Conversion surgery following trastuzumab and docetaxel combination therapy for unresectable HER2-positive parotid gland cancer.

Salivary gland cancers (SGCs) are rare and histologically diverse tumors. Among them, salivary duct carcinoma and carcinoma ex pleomorphic adenoma frequently exhibit HER2 overexpression, for which trastuzumab (Tmab) combined with docetaxel (DTX) has shown clinical efficacy. We report two cases of initially unresectable, HER2-positive parotid gland carcinoma successfully treated with Tmab and DTX, enabling curative surgery. In Case 1, a 68-year-old woman with T4bN2bM0 parotid carcinoma experienced marked tumor shrinkage, allowing surgical resection while preserving the skin and facial nerve. In Case 2, a 46-year-old woman with T4bN2cM0 disease discontinued systemic therapy after four cycles due to toxicity but subsequently underwent successful resection with skin reconstruction. These cases suggest that systemic HER2-targeted therapy can serve as an effective neoadjuvant approach for locally advanced HER2-positive SGCs. Conversion surgery following Tmab and DTX treatment may offer a curative option in selected patients initially deemed inoperable.