Immunohistochemistry is the identification of a cell protein by a specific antibody targeting that protein. It is the most common ancillary test to study the pathology of cancer. Immunohistochemical protein markers are used to differentiate poorly differentiated squamous cell carcinoma from poorly differentiated adenocarcinoma or neuroendocrine carcinomas. They could be used to identify and type the carcinoma in metastatic locations. Importantly, immunodetection of markers also helps in prediction of response to therapies as well as assessing the different biomarkers related to the pathogenesis and clinical behavior of esophageal squamous cell carcinoma. Successful application of the immunochemistry depends on understanding the mechanisms and principles as well as the limitations of the procedure. Automation of the procedure by different models of automatic stainers is widely used in diagnostic laboratories. The use of autostainers streamlines the workflows and certainly reduces the labor, time, and cost of using immunohistochemistry in clinical and research settings.