A new type of microscopy to help scientists examine skin cancers

Summary Ex vivo (meaning that it takes place outside the body) confocal microscopy is an imaging technique which allows scientists to look at samples of skin that have been removed by biopsy (where a small tissue sample is removed surgically), and it is often used to diagnose skin cancers including basal cell carcinomas (BCC). There are two main types, fluorescence confocal microscopy (FCM) and reflectance confocal microscopy (RCM), allowing the visualization of different structures in the tissue sample. FCM requires a stain, a type of dye, to be added to the sample and has been used for the analysis of BCC during a type of surgery called Mohs micrographic surgery (MMS). MMS involves removing a thin layer of the tumour at a time with a very small margin of healthy skin around it, and each layer is immediately checked under the microscope. In RCM, a beam of light is focused on a small area of skin. Varying amounts of this light are reflected back depending on the structure of the cells. This creates a grey‐scale image of a section of the skin which allows doctors to see abnormalities. Recently, a new, faster ex vivo confocal microscope has been developed which uses reflectance and fluorescence simultaneously, providing high‐resolution images in both modes separately and in combination (fusion mode). In this study, the researchers, from Spain, explain which features of a BCC are seen using each of the methods, and if one of the methods is better than the others. They also wanted to develop a new staining protocol to improve the visualization of BCC under the different modes. The researchers used BCCs which were excised (removed) using Mohs surgery in their department. The specimens were first stained with acridine orange and then stained using both acetic acid and acridine orange. Most features were better visualized with the fusion mode using double staining. They also identified new ex vivo confocal microscopy features, dendritic and plump cells, which have not been previously reported. Their results suggest that some features (nuclei characteristics) are better visualized in FCM but others (cytoplasm and surrounding stroma) are better visualized in RCM. For this reason, using both reflectance and fluorescence at the same time, using fusion mode, seems to be beneficial. This summary relates to the study: Basal cell carcinoma characterization using fusion ex vivo confocal microscopy: a promising change in conventional skin histopathology