Morphological Features of the Most Advanced Intra-Tumor Component in Multistep Progression

Advances in basic life science during the past decade have exponentially increased our understanding of the molecular bases of lung cancers and this improved insight has had great effects on diagnosis, prognosis, classification, and treatment of cancer. Similar to colorectal carcinoma, stepwise development of lung cancer has been proposed. For squamous neoplasm, dysplasia is considered to progress to invasive cancer through carcinoma in-situ in association with accumulations of genetic and epigenetic alterations. In lung adenocarcinoma, a preinvasive lesion, termed atypical adenomatous hyperplasia, progresses to an adenocarcinoma in situ, namely a bronchioloalveolar carcinoma, followed by an invasive adenocarcinoma. Currently, molecular alterations, which are involved in each transition, have been also revealed. In this review, I would like to discuss correlation of morphological features with the progression of lung adenocarcinoma with special reference to the most advanced component within the tumor. (J Lung Cancer 2010;9(2):53 �� 56)