Zhang Z, Wang J, Tang P. Breast carcinomas with low ER expression share similar clinicopathological features with ER negative tumors. Mod Pathol. 2013 Feb 1;26(Suppl. 2, Mtg.Abs.314):77A.

BACKGROUND: Positive ER expression is prognostic and predictive for breast cancer patients. Recent ASCO/CAP guideline recommends that the cut off value for ER positivity drops to greater than or equal to 1%. Here, we analyzed various clinical and pathologic factors in different subgroups of breast cancer with different levels of ER expression, with specially emphasis on the low ER expression subgroup.

DESIGN: One thousand and fifty-one cases of invasive breast carcinomas diagnosed at University of Rochester Medical Center between 1999 and 2012 were evaluated. The clinical and pathological data including patient age, tumor focality, tumor size, nodal status, histologic grade, status of lymphovascular invasion (LVI) and perineural invasion (PNI), and expression of ER, PR, HER2 and Ki-67 from each case were recorded. These cases were divided into five subgroups based on the levels of ER expression: ER<1%, ER1-10%, ER11-50%, ER51-70%, and ER>70%. The relationship of clinical and pathologic features between these subgroups was evaluated.

RESULTS: The clinicopathological characteristics (patient age, tumor focality, tumor size, nodal status, histologic grade, status of LVI and PNI, and expression of ER, PR, HER2 and Ki-67) were significantly different when we compared all the five subgroups together. However, the comparison between ER<1% and ER1-10% subgroups showed no statistical difference in tumor size, nodal status, tubular formation, mitosis, expression of HER-2 and Ki-67, and status of LVI and PNL, with exception for patient age, histological grade and nuclear grade. Comparison between ER1-10% and ER>11% showed significant difference in nodal status, histological grade, tubular formation, nuclear grade, mitosis, expression of HER2 and Ki-67, and status of LVI, with exception of patient age, tumor size, status of PNI. Significant difference were also found between ER>70% and subgroups with ER=70%. No significant difference existed between ER 11-50% and ER51-70%.

CONCLUSIONS: Breast carcinomas with Low ER expression (1-10%) represent distinctive subgroup that is associated with more aggressive clinicopathological features in spite of being ER positive. It is more similar to ER negative tumors than to the rest of ER positive groups, and should be managed accordingly. There are significant clinical pathological difference among three groups of breast carcinomas based on levels of ER expression (ER=10%, ER11-70%, and ER>70%). Further studies are needed to investigate the clinical significance among these three groups.

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