Fluorescence Confocal Microscopy During Mohs Surgery
BackgroundEx vivo fluorescence confocal microscopy (FCM) enables real-time imaging of skin morphology directly in freshly excised tissue. FCM displays wide field-of-view mosaics with cellular resolution, thus enabling a rapid bedside pathology. An application of interest is rapid detection of residual basal cell carcinoma (BCC) in skin excisions during Mohs surgery.
Objectives We sought to evaluate the sensitivity and specificity of ex vivo imaging with FCM for the detection of residual BCC in Mohs tissue excisions, and to calculate the time invested up to the diagnosis for both FCM and frozen sections.
Methods Eighty consecutive BCCs were prospectively collected and the margins scanned with ex vivo FCM, including excisions with and without residual BCC of all major subtypes. Each mosaic was divided into two or four, resulting in 480 submosaics for study. Every confocal submosaic was assessed for the presence or absence of BCC and compared with standard frozen sections as the gold standard. Furthermore, the time spent for each technique was calculated and compared.
Results The overall sensitivity and specificity of detecting residual BCC were 88% and 99%, respectively. Moreover, the new technique reduced by almost two-thirds the time invested when compared with the processing of a frozen section (P < 0·001).
Conclusions The results demonstrate the feasibility of confocal mosaicing microscopy in fresh tissue for rapid surgical pathology, potentially to expedite and guide Mohs surgery with high accuracy. This observation is an important step towards the goal of using real-time surgical pathology for skin tumours.
Confocal mosaicing microscopy is an attractive alternative to frozen histopathology during Mohs micrographic surgery (MMS), as cellular morphology can be observed, in real time, in thin optical sections and directly in freshly excised tissue.
In reflectance-mode confocal microscopy (RCM) a strong bright scattering interference comes from the dermis (reflectance), making the diagnosis difficult. However, in fluorescence-mode confocal microscopy (FCM) a contrast agent (acridine orange) specifically stains nuclei, increasing the contrast of nucleated cells, and only weak fluorescence is collected from the dermis.
In confocal mosaicing, high-resolution individual images (750 × 750 μm) are stitched together to create mosaics that display low magnification of large areas of tissue, as required for Mohs surgery. Modern FCM devices are able to display wide field-of-view mosaics of up to 12 × 12 mm; this corresponds to a 2 × view of standard light microscopy, which is the method routinely used by Mohs surgeons when reading frozen sections. Each FCM mosaic is created in < 3 min, enabling real-time bedside pathology.
Recent studies have demonstrated an excellent correlation between ex vivo FCM images and histopathology for nonmelanoma skin cancer. Moreover, the feasibility of rapid bedside pathology with FCM has been widely described, and may represent a time-saving alternative to frozen sections during microscopically controlled surgery.
It has been shown that not only is MMS safe, but it is also the technique with the lowest rates of basal cell carcinoma (BCC) recurrence. However, it is a time-consuming procedure without a proven cost–benefit ratio as yet. In a blind evaluation, residual BCC was detected in freshly excised Mohs tissue with an overall high sensitivity and specificity compared with the gold standard of a frozen section stained with haematoxylin and eosin.
The goal of this study was to calculate prospectively the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of FCM in detecting residual BCC on the surgical margins during Mohs surgery. Although there are a few published reports that have evaluated these parameters, ours is the first prospective study to incorporate ex vivo FCM into daily practice in a Mohs surgery setting. Furthermore, we also sought to calculate and compare the time consumed by FCM vs. frozen pathology, for the first time, during the routine practice of Mohs surgery. Ex vivo FCM is the outstanding advance in Mohs surgery over the last decades and may evolve into an entirely new alternative to classical histopathology, saving time and lowering MMS costs.
Abstract and Introduction
Abstract
BackgroundEx vivo fluorescence confocal microscopy (FCM) enables real-time imaging of skin morphology directly in freshly excised tissue. FCM displays wide field-of-view mosaics with cellular resolution, thus enabling a rapid bedside pathology. An application of interest is rapid detection of residual basal cell carcinoma (BCC) in skin excisions during Mohs surgery.
Objectives We sought to evaluate the sensitivity and specificity of ex vivo imaging with FCM for the detection of residual BCC in Mohs tissue excisions, and to calculate the time invested up to the diagnosis for both FCM and frozen sections.
Methods Eighty consecutive BCCs were prospectively collected and the margins scanned with ex vivo FCM, including excisions with and without residual BCC of all major subtypes. Each mosaic was divided into two or four, resulting in 480 submosaics for study. Every confocal submosaic was assessed for the presence or absence of BCC and compared with standard frozen sections as the gold standard. Furthermore, the time spent for each technique was calculated and compared.
Results The overall sensitivity and specificity of detecting residual BCC were 88% and 99%, respectively. Moreover, the new technique reduced by almost two-thirds the time invested when compared with the processing of a frozen section (P < 0·001).
Conclusions The results demonstrate the feasibility of confocal mosaicing microscopy in fresh tissue for rapid surgical pathology, potentially to expedite and guide Mohs surgery with high accuracy. This observation is an important step towards the goal of using real-time surgical pathology for skin tumours.
Introduction
Confocal mosaicing microscopy is an attractive alternative to frozen histopathology during Mohs micrographic surgery (MMS), as cellular morphology can be observed, in real time, in thin optical sections and directly in freshly excised tissue.
In reflectance-mode confocal microscopy (RCM) a strong bright scattering interference comes from the dermis (reflectance), making the diagnosis difficult. However, in fluorescence-mode confocal microscopy (FCM) a contrast agent (acridine orange) specifically stains nuclei, increasing the contrast of nucleated cells, and only weak fluorescence is collected from the dermis.
In confocal mosaicing, high-resolution individual images (750 × 750 μm) are stitched together to create mosaics that display low magnification of large areas of tissue, as required for Mohs surgery. Modern FCM devices are able to display wide field-of-view mosaics of up to 12 × 12 mm; this corresponds to a 2 × view of standard light microscopy, which is the method routinely used by Mohs surgeons when reading frozen sections. Each FCM mosaic is created in < 3 min, enabling real-time bedside pathology.
Recent studies have demonstrated an excellent correlation between ex vivo FCM images and histopathology for nonmelanoma skin cancer. Moreover, the feasibility of rapid bedside pathology with FCM has been widely described, and may represent a time-saving alternative to frozen sections during microscopically controlled surgery.
It has been shown that not only is MMS safe, but it is also the technique with the lowest rates of basal cell carcinoma (BCC) recurrence. However, it is a time-consuming procedure without a proven cost–benefit ratio as yet. In a blind evaluation, residual BCC was detected in freshly excised Mohs tissue with an overall high sensitivity and specificity compared with the gold standard of a frozen section stained with haematoxylin and eosin.
The goal of this study was to calculate prospectively the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of FCM in detecting residual BCC on the surgical margins during Mohs surgery. Although there are a few published reports that have evaluated these parameters, ours is the first prospective study to incorporate ex vivo FCM into daily practice in a Mohs surgery setting. Furthermore, we also sought to calculate and compare the time consumed by FCM vs. frozen pathology, for the first time, during the routine practice of Mohs surgery. Ex vivo FCM is the outstanding advance in Mohs surgery over the last decades and may evolve into an entirely new alternative to classical histopathology, saving time and lowering MMS costs.
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