The use of neoadjuvant chemotherapy prior to surgical resection for breast cancer is no longer restricted to patients with locally advanced disease. As preoperative treatment becomes more common, the question arises whether or not such therapy changes important tumor characteristics. The objective of our study is to compare histological grade, hormone receptor status, and HER2/neu expression pre- and post-therapy patients receiving preoperative neo-adjuvant chemotherapy. Forty patients status post-neoadjuvant treatment who had available archived pathologic material pre- and post-therapy were identified. Glass slides were reviewed retrospectively, and tumor grade, hormone receptor status, and HER2/neu expression were compared between the pre- and post-therapy specimens. No significant differences were noted between the pre- and post-specimens for two of the three parameters comprising the modified Bloom-Richardson grade, including degree of tubule formation (p = 0.062) and nuclear pleomorphism (p = 0.086). For mitotic activity, a decrease in score was observed between pre- and post-therapy specimens which was statistically significant (p = 0.021). However, there was no significant difference in the overall modified Bloom-Richardson grade (p = 0.118). Information was available regarding hormone receptor and HER2/neu status in 26 patients (65%). There was no significant difference between pre- and post-treatment specimens for hormone receptor status. However, there were more patients with HER2/neu overexpression after receiving neoadjuvant therapy (p = 0.027). Neoadjuvant therapy resulted in a significant decrease in mitotic count and an increase in the proportion of patients with Her2/neu overexpression. No significant changes were noted for the degree of tubule formation, nuclear pleomorphism, overall Bloom-Richardson score, and hormone receptor status. However, small sample size may be a limitation of these results. © 2008 Blackwell Publishing, Inc.