Membranous overexpression of S100A10 is associated with a high-grade cellular status of breast carcinoma.

S100A10 promotes tumor invasion in various cancers. Although genetic studies on S100A10 in breast carcinoma (BC) have been used for molecular biological classification, immunohistochemical studies are lacking. We aimed to identify the correlation between S100A10 expression in BC and various pathological parameters, including morphological features to determine histological grade (HG). Immunostained serial paraffin-embedded tissue sections from 176 cases of resected BC or normal mammary ducts (controls) were assessed for the membrane expression of S100A10. Of the 176 cases, 125 conventional infiltrating ductal carcinomas were chosen, comprising 67 (53.6%) S100A10-positive tumors, whereas normal mammary ducts were S100A10-negative. S100A10 immunoreactivity in ductal carcinoma in situ (n = 51) was similar to that of invasive carcinoma. The distinct membrane-immunopositivity was correlated with high HG, severe nuclear pleomorphism, frequent mitotic counts, high Ki-67 labeling index, HER2/neu overexpression, and low estrogen receptor status (P < 0.05), but not with tubular formation, pT categories, node metastasis, vessel permeation, and pStage. Membrane overexpression of S100A10 in BC correlates with the high-grade morphological and molecular status of the carcinoma cell rather than stromal invasion and architectural deviation. Evidence points to the use of S100A10 as a biomarker representing a high-grade cellular status of BC.