Immunohistochemistry (IH) has revolutionized tumor diagnosis in recent years. The antigenic/molecular information now available is extraordinarily helpful not only in clinical diagnostic work, but also in improving our understanding of the cell biology of neoplasia. As a result, there is now less need for diagnostic conventional transmission electron microscopic (CTEM) studies on neoplasms. For example, lymphomas and leukemias are now largely defined by IH and related techniques such as flow cytometry, not CTEM. A postive S-100 stain in the right setting usually obviates the need to search for melanosomes.

However, CTEM is still a useful tool for surgical pathologists. One important advantage CTEM has over IH is that - like gross observations and the classic H&E section - CTEM can detect features not suspected in advance. This property of CTEM makes it particularly valuable in studying complex and unusual patients/tumors.