Introduction The early detection of lung cancer during bronchoscopy remains a diagnostic challenge. Chromobronchoscopy, using vital dyes, has the potential to aid diagnosis by highlighting areas of dysplastic or malignant change. There are limited numbers of studies in this field but results to date are conflicting. Using a novel electrospray system, we delivered targeted methylene blue (MB) to ex vivo human lung cancer tissue. The aim of this study was to identify whether MB provided a differential stain for lung cancer.

Methods Patients undergoing surgical resection were consented to the study. Following lobectomy, fresh sections of cancerous and non-cancerous tissue were obtained. A range of concentrations of MB were applied topically to tissue sections by electrospray atomisation. Following delivery of MB, the tissue was washed with 0.9% saline and images captured. Results were classified in terms of intensity of dye uptake as well as differential staining between normal and cancerous tissue.

Results 11 patients were included in this study. NSCLC was confirmed in all patients. 7 patients were diagnosed with adenocarcinoma and 4 patients with squamous cell carcinoma. A differential stain for lung cancer versus normal tissue was achieved (Figure 1).

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Abstract S35 Figure 1

Lung cancer (a) and healthy tissue (c) prior to MB delivery. Differential staining of lung cancer tissue (b) following MB delivery and wash. Minimal staining of healthy tissue (d) following MB delivery and wash

Conclusion These findings indicate that MB has the potential to differentiate malignant and healthy tissue in an ex vivo model. This study supports the utility of MB as a potential diagnostic aid in lung cancer surveillance.