Multimodal confocal microscopy for diagnosing nonmelanoma skin cancers

The standard diagnostic procedure for skin cancers is invasive biopsy followed by histopathological evaluation. The biopsy may result in scarring and infection. A reliable way to noninvasively image suspicious lesions with high resolution and contrast would be valuable. In this study, the suitability of dye-enhanced multimodal confocal microscopy for the detection of nonmelanoma skin cancers was evaluated.

For the experiments we used fresh tumor material stained using 0.2 mg/ml or 0.05 mg/ml aqueous solutions of methylene blue (MB) or toluidine blue (TB), respectively. Reflectance, fluorescence, and fluorescence polarization images of skin specimens stained with MB and TB were excited by 656 nm and 633 nm light, respectively. Fluorescence emission and anisotropy were registered between 690 nm and 710 nm. In addition, reference reflectance images at 830 nm were acquired. In total we imaged, analyzed, and compared to histology at least 10 samples of each tumor-type including nodular basal cell carcinoma (BCC), infiltrative basal cell carcinoma, and squamous cell carcinoma (SCC).

The morphological features and appearance of skin structures in the fluorescence images correlate well with corresponding histology for all investigated tumor-types. Multi-spectral reflectance images provide information on the tissue spectral responses and are complimentary to the fluorescence images. The differences detected by fluorescence polarization in cancerous and normal structures may be used for cancerous tissue discrimination. Our results indicate the feasibility of using multimodal confocal microscopy as real-time tool for detecting skin pathology.