A rare case of high-grade intraductal carcinoma of the upper lip: immunohistochemical and genetic analyses.

Although intraductal carcinoma (IDC) of the salivary glands was previously called low-grade cribriform cystadenocarcinoma, it was newly categorized in the 4th version of the World Health Organization classification. We report a case of IDC of the upper lip and examined it immunohistochemically and genetically. The patient was a 48-year-old Japanese female, who noticed a tiny nodule on her left upper lip. Histologically, the tumor cells, which had eosinophilic cytoplasm, exhibited papillary and solid growth patterns, and regions of suspected microinvasion or intraductal spread were also seen at the periphery of the tumor. Small necrotic foci were noted. Immunohistochemically, the tumor cells were diffusely positive for the androgen receptor, CK19, CK5/6, EGFR, and SOX10, whereas they were focally positive for GCDFP-15, S-100 protein, and mammaglobin. The tumor nests were surrounded by alpha-smooth muscle actin-p63-/calponin-/CK14-positive myoepithelial cells. The Ki-67 labeling index was 51.2%. Genetic analysis showed no evidence of the TRIM27-RET or NCOA4-RET fusion gene. We finally diagnosed the tumor as a high-grade mixed intercalated duct/apocrine-type IDC of the upper lip. IDC of the minor salivary glands is exceedingly rare. We discuss diagnostic problems associated with minor salivary gland lesions, and the "basal-like" phenotype of this case.