The prognostic significance of tumor-associated stroma in invasive breast carcinoma Objective: Fibroblasts in the stromal component of a tumor may influence tumor progression in various organs. The prognostic significance of tumor-infiltrating lymphocytes is also frequently reported. However, the prognostic significance of the stromal component in breast cancers, particularly those of high grade, has not been established. Method: In this study, we analyzed surgically resected specimens from 545 patients with breast carcinoma, including 193 high grade tumors, for tumor-stroma ratio, dominant stroma type (collagen (C), fibroblast (F) or lymphocyte (L) dominant type), and central fibrosis on hematoxylin-eosin stained histological sections. We correlated these features with clinical prognosis. Results: Among the 533 specimens examined, 127 (23.3 %) were of C type, 292 (53.6 %) of F type, and 114 (20.9 %) of L type. Central fibrosis was found in 99 tumors (18 %). The dominant stroma type was a significant prognostic factor on univariate and multivariate analyses, together with T classification, nodal status and Bloom-Richardson grade. Tumorstroma ratio and central fibrosis did not predict survival on multivariate analysis. Even in high-grade tumors, relapse-free intervals differed significantly according to dominant stroma type. Conclusion: Conventional hematoxylin-eosin stained tumor slides may contain more prognostic information than previously thought; in particular, the dominant stroma type in invasive breast cancer may potentially be used to predict outcome.