Quantitative immunohistochemical expression of c Kit in breast carcinomas is predictive of patients' outcome

BACKGROUND: c Kit (CD117) expression in tissues has been reported as a relevant target for specific therapy in some human malignancies, but has been poorly documented in breast carcinomas METHODS: The prognostic significance of c Kit in a series of 924 breast carcinomas (mean follow-up, 79 months) was investigated using standardised high-throughput quantitative densitometry of immunohistochemical precipitates in tissue microarrays. RESULTS: c Kit was expressed in 14.7% breast carcinomas ( and in 42 out of 586 node-negative tumours). In univariate analysis, (log-rank test) the score of c Kit expression correlated with poor patient outcome P = 0.02 and particularly in node-negative cases (P = 0.002). In multivariate Cox analysis, c Kit was an indicator of metastasis independent of 25 other concomitantly evaluated markers of prognosis. Logistic regression showed that c Kit ranked 10 out of 25 (P = 0.041), and was included in a 10-marker signature that allowed 79.2% of the patients to be correctly classified in the metastatic or metastasis-free categories independently of hormone receptors and HER-2 status. Interestingly, c Kit was also a significant predictor of metastasis in node-negative tumours ( 2 out of 25 ranking, P<0.0001) and included in a six-marker signature of prognosis, correctly classifying 88.6% of the patients (P<0.0001). CONCLUSION: We concluded that, as assessed by quantitative immunohistochemistry, c Kit is an independent prognostic indicator that could also potentially serve as a target for specific therapy in breast carcinomas. British Journal of Cancer ( 2009) 101, 48-54. doi: 10.1038/sj.bjc.6605113 www.bjcancer.com Published online 9 June 2009 (C) 2009 Cancer Research UK