A comparison of the usefulness of electron microscopy and immunohistochemistry. One laboratory's experience

As a quality assurance measure, the usefulness of transmission electron microscopy (EM) and immunohistochemistry (IHC) in our surgical pathology laboratory was compared. The surgical pathology reports from 150 consecutive neoplasms that were examined by both EM and IHC were reviewed. Based on the reported clinical histories, final diagnoses, light microscopy results, and the findings by EM or IHC, the contributions of EM and IHC were classified as "helpful" or "not helpful" for each specimen. Electron microscopy was helpful (92%) more often than was IHC (73%). Electron microscopy was most useful in further classifying poorly differentiated carcinomas, while IHC was particularly useful in classifying poorly differentiated neoplasms. Electron microscopy and IHC were of limited value in identifying the origin of metastatic carcinomas of an uncertain primary. All cases determined to be "not helpful" by either modality were further analyzed to establish a reason for the lack of information provided in each case. This analysis demonstrated a need for improved technical quality and ordering patterns of immunohistochemical stains in our laboratory.