Maspin mRNA expression in sentinel lymph nodes predicts non‐ SLN metastasis in breast cancer patients with SLN metastasis

Aims Maspin is known to be a tumour suppressor protein, but its prognostic significance in breast cancer patients is controversial. There is no report focusing on maspin expression in metastatic carcinoma of sentinel lymph nodes ( SLN s); we thus investigated maspin mRNA expression in SLN s using the remaining specimens after the one‐step nucleic acid amplification ( OSNA ) assay. Methods and results Ninety‐three breast cancer patients with SLN s metastasis detected by the OSNA assay were enrolled. All patients experienced additional axillary lymph nodes ( LN s) dissection and all dissected LN s were examined histopathologically. Maspin mRNA expression in SLN s was detected in 49.5% (46 of 93) and was correlated significantly with the presence of non‐ SLN metastasis ( P < 0.0001) and ≥4 LN metastases ( P = 0.029). In a multivariate logistic analysis, maspin mRNA expression in SLN s ( P = 0.0015) had the most significant effect on predicting non‐ SLN metastasis, followed by pathological tumour size ( P = 0.0039) and lymphovascular invasion ( P = 0.009). The status of maspin mRNA expression in SLN s was correlated significantly with that of maspin protein expression in the primary carcinoma ( P < 0.0001). Conclusions This is the first study, to our knowledge, demonstrating that maspin mRNA expression in SLN s is an independent predictor of non‐ SLN metastasis and the presence of ≥4 LN metastases in breast cancer patients with SLN metastasis. The investigation of maspin mRNA expression in SLN s using the remaining specimens after the OSNA assay may be useful for predicting the further progression of metastatic carcinoma in breast cancer patients with SLN s metastasis.