Utility of squash smear cytology in fiber-optic bronchoscopic biopsies

Fiber-optic bronchoscopic biopsies yield very small bits of tissue, leading to high false negativity in lung cancer diagnosis, after paraffin embedding.

The aim of the present study is to assess the diagnostic efficacy of squash smear cytology of fiber-optic bronchoscopic biopsies and to compare this with standard paraffin embedded sections and sputum cytology.

A total of 100 suspected cases of lung cancer were subjected to fiber-optic bronchoscopic biopsies. Multiple biopsies from each were divided into two portions. One portion was processed routinely and paraffin sections made. Squash smears were made from the other and stained by Papanicolaou method. The diagnostic efficiency of two methods was compared. A positive diagnosis of cancer by any of the diagnostic modalities initially or during 6 months follow-up was taken as the gold standard.

Out of 100 cases, 91 cases proved to be cancer. The pick-up rate was 0.77 for squash cytology, 0.55 for tissue sections, and 0.31 for sputum cytology. The pick-up was higher for endo-bronchial tumors by all methods. The agreement between squash cytology and tissue sections was 100% for small cell carcinoma and adenocarcinoma and 88% for squamous cell carcinoma.

Squash smear cytology has better pick-up rate than paraffin embedding in fiber-optic bronchoscopic biopsies and should be the preferred method when only one or few bits are available.