The Significance of the Stromal Response in Breast Cancer: An Immunohistochemical Study of Myofibroblasts in Primary and Metastatic Breast Cancer

Background: Gene expression profiling of breast cancer has demonstrated the importance of stromal response in determining the prognosis of invasive breast cancer. The host response to breast cancer is of increasing interest to pathologists and may be a future focus for novel pharmacological treatments. Methods: This study describes the pattern of distribution of stromal myofibroblasts using immunostains for CD10 and smooth muscle actin (SMA) in 50 primary breast cancers and their matched nodal metastases (68.6% nodes positive and 31.4% nodes negative). The stroma within the tumor (intratumoral) and at the advancing tumor edge (peri-tumoral) was studied in both primary and nodal sites. A simple quantitative scoring system was employed for both immunostains. The correlation between expression of these markers by stromal cells and standard pathological prognostic factors of stage, grade, hormone receptor and Her-2 status was analysed. Results: SMA-positive stromal cells were more abundant in peri-tumoral stroma compared with intratumoral stroma in both primary and metastatic lesions. SMA expression in the lymph node metastases showed a significant correlation with tumor stage. SMA expression in peri-tumoral stroma correlated with Her-2 status. Conclusion: The results of this study suggest that myofibroblasts, particularly those expressing SMA, might potentiate the progression of the carcinomatous process especially in nodal metastases. Thus these cells may be a potential therapeutic target.