MINDACT (Microarray In Node-negative and 1-3 positive lymph-node Disease may Avoid ChemoTherapy) randomized trial design. The clinical impact of MammaPrint is being evaluated in MINDACT, a prospective multicenter randomized trial conducted by the European Organization for Research and Treatment of Cancer. The trial compares the recurrence-risk assessment of the 70-gene signature with that provided by Adjuvant! Online in selecting patients for adjuvant chemotherapy. Patients with concordant results are being treated accordingly (high-risk: chemotherapy with or without endocrine therapy, depending on estrogen receptor (ER) status; low-risk: hormonal therapy if ER-positive without chemotherapy). Discordant cases are being randomly assigned to receive adjuvant therapy on the basis of either clinicopathological or 70-gene signature risk assessment. Launched in 2006, the trial intends to confirm the validity of the signature and demonstrate that its clinical use would reduce the number of patients receiving unnecessary treatments, but the results will probably take years to be revealed. Clinico-path, clinicopathological; N, lymph node; N0, lymph node-negative; RANDOM, randomization; TAM, tamoxifen; yrs, years.