Immunohistochemical Markers of Endocrine/Neuroendocrine Tumors

Endocrine cells and tumors can be divided into neuroendocrine and non-neuroendocrine depending on their immunophenotypic and ultrastructural features. Neuroendocrine cells and tumors are members of the diffuse or dispersed neuroendocrine system (DNES), all of which have secretory granules demonstrated by ultrastructural studies. They can also be recognized with broad spectrum neuroendocrine markers such as chromogranin, synaptophysin, and neural cell adhesion molecules. Members of the DNES also produce specific peptides that can serve as target markers for cell and tumor identification. Non-neuroendocrine tumors include a short list, namely, adrenal cortical cells, thyroid follicular cells, and steroid producing cells of the ovary and testes. Markers such as inhibins are useful for detecting adrenocortical cells and tumors and gonadal tumors, whereas thyroglobulin is relatively specific for thyroid follicular cells. Although immunohistochemical markers are most useful in characterizing and diagnosing endocrine lesions, in situ hybridization can add another level of specificity to these studies because some tumors may take up proteins nonspecifically or may not store sufficient amounts of the protein markers to be detectable by immunohistochemistry. The messenger RNA can be readily detected by in situ hybridization. The use of general and specific markers has provided a great deal of insight into the characterization of endocrine cells and tumors.