Recent experimental data have clearly demonstrated that fibroblast growth factor (FGF)8 plays a key role in the development of human prostate and breast cancers. However, little is known about the FGF8 expression profile in human breast cancer specimens. In this study, we analyzed FGF8 expression in 78 surgically resected specimens of breast cancer using an immunohistochemical method. In total, FGF8 expression was found in 40 (51.3%) of the breast carcinomas. FGF8 expression was not associated with any of the general clinicopathological parameters, including age, tumor size, histological grade, and histological type. In addition, there was no correlation between FGF8 expression and either c-erbB-2 overexpression or the status of the axillary lymph-node metastasis, both of which have been established as important prognostic factors in breast carcinomas. While no significant association was found between FGF8 expression and estrogen- or progesterone-receptor status, it is of interest that FGF8 expression was significantly associated with androgen-receptor status and the expression of prostate-specific antigen (PSA), one of the androgen-regulated proteins, in human breast carcinomas. These associations support the reported in vitro data demonstrating the regulation of FGF8 by androgens, and also suggest that PSA may be a useful marker for patients with FGF8-expressing breast carcinomas.