The biological and chronological evolution of lung cancer remain to be fully elucidated. A multi-step carcinogenesis hypothesis suggests a progression from atypical adenomatous hyperplasia (AAH) through bronchioalveolar carcinoma (BAC) to invasive adenocarcinoma (AC), but to date this has not been formally demonstrated. We report a case of a patient diagnosed by computed tomography (CT) with lung cancer in the superior right lobe who also presented with a pure ground-glass opacity (GGO) in the inferior lobe, while the middle lobe appeared normal. Following pneumonectomy, cytogenetic analysis successfully performed on spontaneous metaphases obtained by the direct method from samples of the three lung lobes showed the presence of three clonal cell populations, each progressively having increased karyotype complexity. Fluorescence in situ hybridization (FISH), performed using ALK (2p23) break probe and ALK/EML4 t(2;2);inv(2) fusion probe, showed a normal pattern for all specimens. Histological evaluation confirmed the presence of AC in the superior right lobe and classified the GGO lesion as BAC and the normal tissue of the middle lobe as AAH. To the best of our knowledge, this is the first case in which the cytogenetic study of spontaneous metaphases showed a clear clonal relationship among AC, BAC and AAH present simultaneously in different lobes of the same lung. This case appears to indicate that the entire lung was somehow predisposed to a neoplastic transformation starting with a diffuse AAH characterized by high proliferative activity. Moreover, the 5q13 region involved in the translocation shared by BAC and AC contains at least 4 genes encoding important regulators of the cell cycle that may be considered new molecular markers of lung cancer.
Keywords: lung cancer, ground-glass opacities, chromosome abnormalities, multi-step progression