Major Pathologic Response in Patients Treated for Non-small Cell Carcinoma of the Lung: Is There a Magic Number in the Histologic Sections to Be Evaluated?

Over the last years, great advancements have taken place in the medical approach to lung non-small cell carcinomas. Currently, with the use of biomarkers and diagnostic molecular pathology, tumors that in the past were treated with conventional chemotherapy, radiation therapy, or both, now similar patients afflicted by non-small cell carcinoma may have other alternative treatments. More importantly, because of those advancements in treatment options, it has become imperative that pathologists not only become familiar with the pathologic response to those treatments but also attempt to provide a pathologic assessment of the different changes that may be present as a result of a particular treatment. Even though for pathologists the demonstration of tumor necrosis and other inflammatory responses because of therapy as well as residual tumor does not represent a difficult task to accomplish, the issue is not in the diagnostic histopathologic assessment but in providing an adequate assessment of tumor viability as well as tumor necrosis and other histopathologic changes. More interesting is to acknowledge that it is in this particular area in which there may be differences in the approach because of the lack of a universal approach regarding how much of a particular tumor needs to be examined. Needless to say, the number of histologic sections examined may at the end be used as a specific parameter for tumor response to a particular treatment. The current review, will highlight, the different methodologies that over the years have been used or employed in the assessment of what is now referred as major pathologic response.