Podoplanin expression in cancer-associated fibroblasts predicts unfavorable prognosis in node-negative breast cancer patients with hormone receptor-positive/HER2 - negative subtype.

Background: Podoplanin expression in cancer-associated fibroblasts (CAFs) has been proposed as an indicator for poor prognosis in patients with invasive breast carcinomas, but little is known about its clinical significance in node-negative breast cancer patients with hormone receptor (HR) + /HER2  - subtype, who are expected to have a favorable prognosis.

Methods: Immunohistochemical analyses were performed on 169 resected specimens of node-negative invasive carcinoma of no special type with HR + /HER2 - subtype using antibodies for podoplanin. When more than 10% of CAFs showed immunoreactivity with podoplanin as strong as that of internal positive controls, the specimens were judged as podoplanin-positive.

Results: Podoplanin-positive status in CAFs was observed in 16.0% (27 of 169 cases) and it associated with high Ki67 labeling index (LI) (> 30%) (p = 0.03), higher stromal tumor-infiltrating lymphocytes (p < 0.001) and progesterone receptor-negative status (p = 0.045). Log-rank test showed that podoplanin-positive status in CAFs correlated with shorter disease-free survival (DFS) (p = 0.007) and disease-specific survival (DSS) (p < 0.001). Univariate analysis showed a significant correlation between shorter DFS and podoplanin-positive status in CAFs (hazard ratio [HR] = 3.380; p = 0.012), the presence of lymphatic invasion (HR = 5.621; p < 0.001), high Ki67 LI (HR = 5.217; p < 0.001), and histological grade III (HR = 3.748; p = 0.008). According to Cox multivariate analysis, podoplanin-positive status in CAFs had the most significant effect on shorter DSS (HR = 37.759; p = 0.003) followed by high Ki67LI (HR = 27.664; p = 0.007).

Conclusion: Podoplanin expression in CAFs could be an independent predictor for poor prognosis in node-negative breast cancer patients with HR + /HER2 - subtype.