Lead with your gut: research‐implicated infant gut staphylococcal strains may predict development of atopic dermatitis

nostic accuracy study includes 753 specimens from 127 patients with basal cell carcinoma (BCC) on the head and neck, and reports 79 8% sensitivity and 95 8% specificity when comparing FCM with frozen-section histopathology. While most BCCs can be removed successfully by simple excision, large BCCs (> 2 cm) and those occurring at some sites (e.g. nose, ear, eyelid, eyebrow) are at higher risk of incomplete removal. In the U.K., the recommended treatment for these ‘high-risk’ BCCs is Mohs micrographic surgery. Although Mohs surgery achieves the lowest recurrence rates and best cosmetic outcomes for patients with ‘high-risk’ BCCs, this surgery requires intra operative preparation of frozen sections, which is time-consuming and labour-intensive, and needs dedicated laboratory infrastructure. Recently, optical microscopy techniques have been proposed as faster alternatives to frozen-section histopathology. Optical microscopy relies on detecting morphological or molecular differences between BCC and healthy skin without the need for tissue sectioning. While FCM has been investigated previously for Mohs surgery, Longo et al. evaluate in a clinical setting the performance of FCM compared with conventional frozen-section and permanent-fixation histopathology using a large number of patients and tissue specimens. One of the strengths of FCM is the ability to acquire highresolution images of the surface of the excised specimen within a few minutes without requiring tissue sectioning. This could transform Mohs surgery, as several layers of skin, or potentially the entire tumour, could be resected within a single anaesthetic dose, reducing the need to move patients in and out of the operating room. The specificity of FCM was found to be high (95 8%) but the 80% sensitivity can be considered modest and is likely to be a barrier for wider adoption. A high sensitivity is paramount for ensuring complete excision of the cancer; failure to ensure that the whole cancer is removed has been linked to higher recurrence rates and the need for re-excision, leading to anxiety for patients and increased healthcare costs. One of the main limitations of the study is that the FCM images were acquired and assessed by a single user. FCM requires additional training for the user to recognize specific morphological features in order to provide a diagnosis, which can lead to diagnosis subjectivity. Technical issues related to bleaching of the fluorescence signals, as indicated by the authors, may contribute to additional diagnosis variability. It is important therefore that future studies include additional users to quantitatively evaluate the inter-user repeatability of FCM. Despite these limitations, this single-site study represents an important step towards implementing new technologies for margin assessment during Mohs surgery. While FCM is clearly faster than frozen section, providing the prospects for speeding up surgery, important improvements in accuracy are needed for a wider clinical adoption. One approach could be, as the authors suggest, the integration of FCM with other optical techniques, which may provide the additional increase in sensitivity. Conflicts of interest