Electron microscopic examination of cytologic samples.

Objective: To review the results of observations of cytologic samples performed in our laboratory by light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) performed in succession (LM-SEM-TEM examination) using the same cytologic sample and to assess the diagnostic value of this method of successive examination.

Study Design: Using a previously reported method of LM-SEM-TEM sample preparation and observation, we analyzed 201 cytologic specimens over a seven-year period (1986-1993) and investigated whether the histologic origin and malignancy can be estimated from SEM and TEM findings on the cells.

Results: Observations of many cytologic samples over a seven-year period (by LM, SEM and TEM) showed that several basic interpretations of cellular ultrastructure are possible. In cases where cell identification was difficult by LM, electron microscopic findings were sometimes useful for determining the biologic characteristics of cells and for estimating their tissue origin. Electron microscopic findings also provided important information for cytodiagnosis.

Conclusion: SEM and/or TEM findings are useful for determining the morphologic (including biologic) characteristics of cells in cases where they cannot be determined by LM. With the accumulation of data on electron microscopic examination of cytologic samples, it is expected that in the future, electron microscopy will continue to provide new information that can be used to improve the accuracy of cytodiagnosis by LM.