Identification of pathogenic macrophages in breast cancer as markers of tumor aggressiveness.

1043 Background: Proliferating macrophages (promacs) are considered to be pathologic. We previously reported high promacs in estrogen receptor (ER) negative, high grade breast cancers with early recurrence. Given the technical complexities of double staining for promacs, we tested another macrophage marker associated with tumoral invasion in several cancer types, Mac387. We asked whether or not Mac387 would identify promac-rich tumors with early recurrences, and therefore, be a simpler potential marker to assess the impact of macrophage targeted drugs in breast cancer. Methods: We obtained fixed breast tumor tissue from 367 patients from UCSF, California Pacific Medical Center, Highland Hospital (Oakland, CA), Abia State University (Aba, Nigeria), and Ghana. Immunohistochemical stains for Mac 387 were read by two independent pathologists. Mac387 staining was dichotomized as 10% of a high powered field (hpf) and was compared to previously obtained promac counts ( >5 promacs/hpf versus <5 promacs/hpf)...