ABSTRACT
Lung cancer is currently the most common cause of cancer incidence and mortality worldwide.1 In 2004 it is estimated that lung cancer will account for over 173000 new cases in the United States and over 160000 cancer deaths.2 While lung cancer incidence has been decreasing in males since the early 1980s, it appears to be near its peak and starting to decline in women.2 Despite all of the efforts at treatment of lung cancer, the 5year survival has remained between 10-15% over the past few decades.3,4 For this reason, there is great interest in early detection of lung cancer utilizing a variety of approaches including fluorescence bronchoscopy and screening of high-risk patients by spiral or helical CT.5,6 Along with the interest in early diagnosis of lung cancer there has been considerable evolution in the concepts of preinvasive lesions for lung carcinoma in the past few decades as well as in lung cancer classification.7,8 This is reflected by the absence of preinvasive lesions in the 1967 WHO classification, the addition of squamous dysplasia/carcinoma ‘in situ’ in the 1981 classification and the addition of atypical adenomatous hyperplasia and diffuse idiopathic neuroendocrine cell hyperplasia in the 1999 and 2004 WHO classifications (Table 5.1). While minor changes were made in
1967 WHO classification84
1981 WHO classification85
1999 WHO/IASLC classification7
2004 WHO classification7,8
classification of several invasive tumors in the 2004 WHO classification compared to the 1999 WHO classification, there were no changes made with regard to preinvasive lesions.
