Hsieh MS, Lee YH, Jin YT, et al. - Researchers analyzed 9 intraductal carcinomas (ICs) (including 3 pure ICs, 6 ICs with invasive carcinoma) and 24 conventional salivary duct carcinomas (SDCs) in this study by performing immunohistochemistry and mutation analyses (including HRAS/PIK3CA mutations, RET rearrangement, and human epidermal growth factor receptor 2 amplification) and then compared the results. Positivity for SOX10 and S100 and negativity for AR was exhibited by four intercalated duct-type cases; five apocrine-type cases demonstrated opposite results. In all five apocrine-type cases, the presence of cysts with relatively circumscribed tumor borders and morphologically mimicking breast low-grade ductal carcinoma in situ or papillary carcinoma was detected. Overall, the apocrine-type IC was found to exhibit different cytological grades, distinct tumor growth patterns, and had no evidence of low- to high-grade transition. Based on these data, experts recommended differentiating apocrine-type IC from apocrine SDC with an in situ component.