Breast lesions defined C3 at ultrasound (US)-guided fine needle aspiration cytology (FNAC) are probably benign, but exhibit atypias. We evaluate the results of US-guided vacuum assisted breast biopsy (VABB) of these lesions. Patients diagnosed C3 by US-FNAC, submitted to US-VABB and with a minimum follow-up of 36 months or surgery were enrolled. Cost outcome of this diagnostic protocol was evaluated. We evaluated 138 patients with non-palpable C3 lesions. In 2/138 (1.4%) cases VABB results were inadequate. VABB diagnosed: 17/138 (12.3%) malignant and 119/138 (86.2%) benign lesions. In 28/138 cases (20.3%) surgery retrieved 18/28 (64.3%) malignant lesions. One false negative result of VABB was observed. Sensitivity and specificity of VABB resulted 94.4% and 100%. Our diagnostic algorithm estimated a 45% mean decrease of costs using VABB when compared with surgical biopsy of all C3 lesions.