Low-grade intraductal carcinoma (low-grade cribriform cystadenocarcinoma) with tumor-associated lymphoid proliferation of parotid gland.

We report a rare case of low-grade intraductal carcinoma with tumor-associated lymphoid proliferation (TALP) in the parotid gland of a 75-year-old woman. Grossly, the tumor was solid and cystic. Histologically, the tumor consisted of a papillary-cystic, micropapillary, or focally cribriform proliferations of epithelial cells with low-grade cytological atypia. The interspaces between the epithelial components were filled with prominent lymphoid stroma and lymphoid follicles, superficially mimicking Warthin tumor. The neoplastic epithelial cells were positive for S100 protein by immunohistochemical staining. There was an attenuated layer of myoepithelial cells all around the epithelial components, indicating a non-invasive (in situ) nature. Although TALP is a rare finding in intraductal carcinoma, it should be considered as a histological variation of this kind of tumor. The relationship between intraductal carcinoma, low-grade cribriform cystadenocarcinoma, low-grade salivary duct carcinoma, and salivary duct carcinoma in situ is also discussed in this report.