Salivary Duct Carcinoma of the Parotid Gland Originating from an Epithelial-Myoepithelial Carcinoma: Report of a Rare Case
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Salivary duct carcinoma (SDC) is a high-grade carcinoma with poor prognosis, especially among various salivary carcinomas. In this study, we report a rare case of SDC of the parotid gland originating from an epithelial-myoepithelial carcinoma (EMC). A 71-year-old Japanese man presented with swelling of the right parotid region and a right facial nerve paralysis for 10 months. He underwent extended total parotidectomy and chemoradiotherapy after the surgery. Histologically, a major part of the tumor was an androgen receptor (AR)-positive, human epidermal growth factor receptor 2 (HER2)-positive, gross cystic disease fluid protein-15 (GCDFP-15)-positive SDC, with a focus of a typical EMC component at the periphery of the lesion. In the transitional area of the two components, inner ductal cells of double-layered ducts showed similar morphology and immunophenotype to SDC. These findings suggest that SDC originated from the inner ductal cells of EMC. Because the tumor included an EMC as a low-grade carcinoma and an SDC as a high-grade carcinoma, we can consider our case as a dedifferentiated carcinoma as well as a hybrid tumor.
KeywordsSalivary duct carcinoma Parotid gland Epithelial-myoepithelial carcinoma Dedifferentiation
The authors thank all medical technologists (Osaka International Cancer Institute) for their technical assistance and Editage (http://www.editage.jp) for English language editing. No funding obtained.
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Conflict of interest
The authors declare that they have no conflict of interest.
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