DS24 Prospective study comparing ex vivo confocal laser scanning microscopy and frozen section histopathology of 23 basal cell carcinomas treated with Mohs micrographic surgery

Abstract

Abstract Ex vivo confocal laser scanning microscopy (CLSM) is an emerging technique that is used for the rapid analysis of freshly excised tissue during Mohs micrographic surgery (MMS). Previous studies on fluorescence CLSM have shown 88% and 99% sensitivity and specificity, respectively, of diagnosing basal cell carcinomas (BCCs) vs. conventional histology. The fourth-generation Vivascope 2500 allows fresh tissue to be scanned after minimal preparation with acetic acid and acridine orange, creating digitally coloured mosaic images, mimicking conventional histological haematoxylin and eosin slides. The scanning speed of < 3 min creates the potential to improve patient experiences, allowing multiple stages and repair in a single session, reducing overall operating times and improving efficiency. After a 2018 pilot study on a limited case series, we have begun the process of testing the real-world use of this technology. We present an initial prospective case series to assess BCC excision of stage 1 Mohs specimens using the Vivascope 2500 vs. conventional frozen section histology. Caldicot approval was sought. Over a 3-month period, 23 cases of stage 1 facial BCCs on one Mohs list were processed. Samples were obtained as standard bevelled Mohs excisions, and Mohs maps were created for all cases. There were three false-negative BCCs, of which two were infiltrative BCCs with small foci missed on the initial review on CLSM images and one superficial BCC not visible due to lack of epidermal capture. Of the four false-positive cases, the foci appearing to be BCC included inflammation in one, follicular structures in two and conjunctival glands misinterpreted as BCC in one eyelid case. Time taken to process specimens and read the digital images by CLSM was compared with the time taken to obtain and read frozen section slides. The shortest time recorded for CLSM and frozen sections was 6 min and 31 min, respectively. The longest time recorded for CLSM and frozen sections was 20 min and 57 min, respectively. In summary, CLSM shows promise in MMS for selected BCCs. Improved techniques to flatten the epidermis for better visualization and further experience with image reading and interpretation have the potential to minimize errors.