Application of low-vacuum scanning electron microscopy in cytopathology: To what extent can adenocarcinoma be morphologically distinguished from squamous cell carcinoma in lung cancer?

Background: Anticancer drugs for targeted molecular therapies have been applied to the treatment of lung cancer. Since the effects of medicine for adenocarcinoma (ADC) or squamous cell carcinoma (SQCC) differ, the ability to discriminate these lesions is important. In the present study, we examined whether ADC and SQCC could be distinguished using low-vacuum scanning electron microscopy (LVSEM) to examine cytopathological specimens.

Methods: Thirty-seven cases of bronchoscopic samples were retrospectively examined using LVSEM on the surface structures of the cancer cells.

Results: Among the Pap-stained slides, 81.1% of the cases could be distinguished: 96.2% of the ADC cases were distinguishable, and 45.5% of the SQCC cases were distinguishable. Among the significant findings for ADC using LVSEM, a spherical shape (73.1%), long filaments (65.4%), dense filaments (80.8%), and depression (57.7%) were seen. Among the significant findings for SQCC as observed using LVSEM, however, a flat shape (81.8%), sparse filaments (72.7%), and non-filament (81.8%) were seen. The overall accuracy of diagnosis using LVSEM was 83.8%: 80.8% for ADC and 90.9% for SQCC. The accuracy of a combination of Papstained slides and LVSEM was 97.3%.

Conclusions: The LVSEM method is useful as an ancillary examination for cytopathology after the classification of Pap-stained slides.