Topographical distribution of allelic loss in individual lung adenocarcinomas with lymph node metastases

Adenocarcinomas of the lung are characterized by morphological heterogeneity, and since carcinogenesis has been suggested to be a multistep process involving sequential accumulation of multiple genetic alterations, the morphological heterogeneity may represent a cross-sectional view of genetic alterations within individual tumors. Therefore, to elucidate whether, and which, genetic alterations accumulated in relation to morphological cancer progression, we examined 56 microdissected sites for topographical distribution of loss of heterozygosity (LOH) in 12 adenocarcinomas of the lung with bronchioloalveolar (BA) and invasive components in their primary tumors and metastases to lymph nodes. The morphological changes from noninvasive BA lesions to invasive and metastatic components were characterized by a significant rise in the prevalence of allelic losses (P<0.05). Individually, eight cases (67%) showed accumulation of genetic alterations from BA lesions to metastases. LOHs in multiple foci in one case were compared to determine whether they were shared at all tumor sites as an early event or localized in metastases as an additional event. LOHs at 5q and 17p may be crucial steps in the early phase of development to metastasis, while 18q loss may be an additional step. These findings suggested that the cancer cells in some pulmonary adenocarcinomas evolved from the BA lesions to the invasive and metastatic lesions.