CD56 Antibody: Old-Fashioned or Still Trendy in Endocrine Lung Tumors

In 2010, the World Health Organization published a new classification of the endocrine tumors based on the mitotic rate and index. Concerning lung endocrine tumors, the classification of 2004 remains acceptable and widely approved. We noticed in many publications that the most used antibodies in these tumors are chromogranin and synaptophysin. This finding let us wonder about the diagnostic utility of the CD56 antibody which is widely used in our department.Sixty-nine endocrine lung cancers were diagnosed over a 12-month period in our Department of Pathology. Immunohistochemical technique using the three antibodies: chromogranin, synaptophysin, and CD56 was performed. The sensitivity of the three antibodies was performed using the ratio: true negative cases/true negative cases + false positive cases. The specificity wasn't performed because the antibodies were used only in endocrine tumors. The comparison of the different percentages of expression of the three antibodies was made by the SPSS software 22.0.The sensitivity of the chromogranin, synpatophysin, and CD56 accounted for 69%, 77%, and 98%, respectively. The mean percentage of immunoreactive cells with CD56 was 70% towards 15% and 20% with chromogranin and synaptophysin antibodies, respectively. The comparison of the percentages of expression showed a significant statistical difference between the expression of CD56 versus synaptophysin and CD56 versus chromogranin with P<0.001.CD56 antibody seems to be of diagnostic value in endocrine lung tumors with the highest sensitivity. This fact highlights the necessity of using it as a first-line neuroendocrine marker in association to chromogranin which is considered as the most specific endocrine antibody.