[Expression of pS2-protein in breast cancer]

We studied the relationship between pS2-protein and estrogen receptor in breast cancer tissue immunohistochemically using paraffin-embedded sections obtained from 96 primary breast cancer tissues in which the estrogen receptor had been examined by ERICA using frozen section. ER-negative breast cancer specimens were negative for pS2 in 85% of the cases, and ER-positive breast cancers were positive for pS2 in 66% of the cases, the entire concurrence rate between pS2 and ER being 73%. Although the agreement was statistically significant, it seemed to be unreasonable that pS2 could replace ERICA in the routine detection of ER. However, the cases with pS2 stained (+2) or (+3) might be ER positive. pS2 showed a positive correlation to ER and PgR, and negative correlation to p53. This suggested that pS2 is a prognostic factor in breast cancers. Our findings suggested that pS2 also is a new marker of hormonal therapy for breast cancer.