The pathogenesis of lung cancer has not been fully elucidated and biological markers acting as predictors of tumor evolution and aggressiveness remain unidentified. The multi-step hypothesis, suggesting a progression from adenomatous hyperplasia (AAH) to adenocarcinoma (AC) through bronchioalveolar carcinoma (BAC), was highlighted in a previous cytogenetic study performed in a single case. The present study reports the results of an array-comparative genomic hybridization (a-CGH) analysis performed on the DNA obtained from the previously reported case that presented AAH, BAC and AC in one lung. The a-CGH results confirm and support the previous cytogenetic observations with new data, clearly supporting the hypothesis of a multi-step carcinogenic process in the lung.