Dissemination of tumor cells along the needle tract after needle aspiration biopsy has been reported in the literature, but it is an extremely uncommon event, especially when 'fine needles' (above 21 Gauge) are used. In the work presented, a patient with a mammary nodule of doubtful nature is reported. After histological evaluation the node proved to be an intra-mammary dissemination of poorly differentiated adenocarcinoma of the lung via the needle track after aspiration biopsy. The needle used was a 20 Gauge, which is not included in the fine needle category recommended by most authors. The possibility of tumor cells dissemination after needle biopsies is discussed.