Electron microscopy as a tool in the diagnosis of endocrine tumors

Electron microscopy (EM) has provided a large amount of information toward the discovery of endocrine cell systems and the analysis of endocrine tumors. In the diagnosis of endocrine tumors EM is most often not decisive. This is due to sampling errors, tumor cell diversity, pleomorphism of cellular organelles, particularly of secretory granules, and to the lack of reliable structural markers of biologic behaviour of tumor cells. For diagnostic purposes EM has been superseded by immunocytochemical techniques, and in the near future recombinant DNA technology will probably lead to further progress in the precision of analysis of hormone production by tissues, cells and tumors. On the other hand, EM combined with other techniques is a powerful tool in research.