Objectives: To evaluate the underestimation rate and clinical relevance of lobular neoplasia in vacuum-assisted breast biopsy (VABB)., Methods: A total of 161 cases of LN were retrieved from 6,435 VABB. The histological diagnosis was ALH (atypical lobular hyperplasia) in 80 patients, LCIS (lobular carcinoma in situ) in 69 patients and PLCIS (pleomorphic lobular carcinoma in situ) in 12 patients. Seventy-six patients were operated on within 2 years after VABB and 85 were clinically and radiologically monitored. The mean follow-up was 5.2 years, and the prevalence of malignancy was evaluated in the group of 85 patients., Results: The clinico-pathological characteristics significantly favouring surgery were larger lesions, occurrence of a residual lesion following VABB and histological LCIS and PLCIS subtypes. The VABB underestimation rate as compared to surgery was 7.1% for ALH, 12% for LCIS and 50% for PLCIS. Overall, 11 of the 148 patients included in this survival analysis developed an ipsilateral tumour., Conclusion: Although obtained retrospectively in a relatively small series of patients, our data suggest that only patients with a diagnosis of PLCIS in VABB should be treated with surgery, whereas patients with ALH and LCIS could be monitored by clinical and radiological examinations., Key Points: • The treatment of ALH and LCIS in VABB is still debated • Some authors favour radical treatment and others a more conservative approach • Only patients with PLCIS in VABB should be treated by surgery.