Diagnosis of lung cancer - Pathology of invasive and preinvasive neoplasia

The histopathologic appearance of lung carcinoma remains an important guide to prognosis and treatment. The newly revised World Health Organization cl assification retains the broadest pathologic categories of the older classi fication but includes several revisions, including the elimination of the s mall cell, intermediate cell type category; the addition of large cell neur oendocrine and spindle/giant cell categories; and an extended consideration of preneoplastic lesions. The histopathologic classification of lung cance r is expected to continue to change as clinical practice and biological und erstanding of these tumors change. The application of immunohistochemical t esting to histologic material not only provides new assistance with convent ional histologic classification, but also permits new ways to subclassify t umors, the full clinical significance of which is yet to be realized. The s ignificance of expression of neuroendocrine markers, histologic grading of response to chemotherapy, and delineation of morphologic changes preceding the occurrence of invasive carcinoma are all areas where understanding micr oscopic cellular changes in the airways will be critical for clinical advan ce.