Ex Vivo Confocal Microscopy: Revolution in Fast Pathology in Dermatology

J. Malvehy; J. Pérez-Anker; A. Toll; R. Pigem; A. Garcia; L.L. Alos; S. Puig

Disclosures

The British Journal of Dermatology. 2020;183(6):1011-1025. 

In This Article

Barriers and Future Advances in Ex Vivo Confocal Microscopy

The first ex vivo CM devices gave inferior results compared with conventional histological examination because the cytological and architectural details could not always be clearly identified. At that time the images were based on a single mode of greyscale contrast and appeared black and white, whereas histology is based on two stains (haematoxylin for nuclei and eosin for cellular cytoplasm and dermis) and appears purple and pink. With the new devices, digital staining from fusion images of RCM and FCM modes could be used in order to change the greyscale into a colour scale that reproduces the colours and structures in H&E histology. In recent studies with new and faster microscopes, in just a few minutes, images similar to H&E staining exhibited superior histopathological correlation compared with old devices. Ex vivo CM using new microscopes has a higher resolution at the cellular level, and it seems that this method can be adopted for pathological diagnosis in a number of conditions in which the cellular and architectural abnormalities have been well described. However, prospective studies in Mohs surgery assessing the recurrence rate after surgery using ex vivo CM are lacking at the time of this review.

Recently a new line of scanning, the line scanning, stage scanning confocal microscope (LSSSCM), was used in BCC by Gareau et al. using a 488-nm and 532-nm coherent sapphire laser and orange acridine as a staining method.[76] LSSSCM uses no scanning mirrors and has the advantages of a faster scan with cellular resolution and lower manufacturing cost. LSSSCM is a new, promising candidate for clinical translation of rapid pathology and surgical guidance given the clinical demand and potential multimodality, supporting H&E-like colourization.

One of the main limitations of ex vivo CM has been the lack of specific cellular staining. Recently a few publications have tested specific stains for cell subtypes in melanoma or in cutaneous vasculitis that will open up the way for new applications. In this case, the main advantage of time in ex vivo CM compared with standard pathology may not be obvious, as the preparation and staining of the antibodies needs at least 2 h. Outside the realms of dermatology, ex vivo CM has also been extended to other disciplines that might require extemporaneous examination of tumours, such as prostate, brain, breast and thyroid tumours.

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