Expression of transcription factor ZEB1 in sarcomatoid salivary duct carcinoma of the parotid gland

Recent studies have identified the epithelial mesenchymal transition-inducing transcriptional repressor ZEB1 as promoting invasion, metastasis, and stemness in aggressive cancers and causing resistance to cancer therapy. We present a study of aberrant ZEB1 expression in a case of salivary duct carcinoma harboring sarcomatoid elements. A 60-year-old man presented with a mass, which rapidly grew in the right parotid gland; the patient underwent surgical resection. The mass extended widely, into the adipose tissue surrounding the parotid gland, with regional lymph node metastasis. Histopathological examination revealed that the tumor resembled ductal carcinoma of the breast, with comedo-like necrosis, and elements of invasive-growth adenocarcinoma. Immunohistochemical study revealed HER2/neu, androgen receptor, and mammaglobin immunoreactivity in the cancer cells. Furthermore, we found a sarcomatous element, highlighted by pleomorphic spindle-shaped cells with marked nuclear atypia, in the tumor. Based on these histopathological features, we considered the tumor to be a sarcomatoid variant of salivary duct carcinoma. Further immunohistochemical analysis showed that not only sarcomatoid tumor cells, but also epithelial tumor cells, including intraductal carcinoma-like cells, exhibited immunoreactivity with a specific antibody to ZEB1. Notably, ZEB1 immunoreactivity was also found in non-sarcomatoid salivary duct carcinoma of other patients. In contrast, intraductal components of breast cancer from other patients did not show ZEB1 immunoreactivity. Our findings might indicate that "ductal carcinoma of breast-like cells", in both sarcomatoid variants and non-saromatoid type of salivary duct carcinoma, expressed ZEB1, and thus, had a greater potential to be aggressive compared to morphologically similar breast cancer cells.