Confocal mosaicking microscopy (CMM) enables rapid imaging of large areas of fresh tissue ex vivo without the processing that is necessary for conventional histology. When performed in fluorescence mode using acridine orange (nuclear specific dye), it enhances nuclei-to-dermis contrast that enables detection of all types of basal cell carcinomas (BCCs), including micronodular and thin strands of infiltrative types. So far, this technique has been mostly validated in research settings for the detection of residual BCC tumor margins with high sensitivity of 89% to 96% and specificity of 99% to 89%. Recently, CMM has advanced to implementation and testing in clinical settings by “early adopter” Mohs surgeons, as an adjunct to frozen section during Mohs surgery. We summarize the development of CMM guided imaging of ex vivo skin tissues from bench to bedside. We also present its current state of application in routine clinical workflow not only for the assessment of residual BCC margins in the Mohs surgical setting but also for some melanocytic lesions and other skin conditions in clinical dermatology settings. Last, we also discuss the potential limitations of this technology as well as future developments. As this technology advances further, it may serve as an adjunct to standard histology and enable rapid surgical pathology of skin cancers at the bedside.

Importance Extramammary Paget disease (EMPD) is commonly refractory to surgical and nonsurgical therapies. Identifying recurrent or persistent EMPD is challenging because the disease is multifocal, and multiple blind scouting biopsies are usually performed in this setting. Handheld reflectance confocal microscopy (HRCM) has been used to diagnose and map primary EMPD and therefore may be used to identify EMPD recurrences. Objective To evaluate HRCM’s diagnostic accuracy in the setting of recurrent or persistent EMPD as well as its potential diagnostic pitfalls. Design, Setting, and Participants This prospective case series study included patients referred to the Dermatology Service at Memorial Sloan Kettering Cancer Center between January 1, 2014, and December 31, 2016, with biopsy-proven EMPD in whom HRCM was used to monitor treatment response. Five patients were included, and 22 sites clinically concerning for recurrent or persistent disease were evaluated using HRCM and histopathologic examination. In 2 patients, video mosaics were created to evaluate large areas. Main Outcomes and Measures Sensitivity and specificity of HRCM in identifying recurrent or persistent EMPD; causes for false-negative results according to their location, histopathologic findings, and previous treatments. Results Of the 22 clinically suspicious sites evaluated in 5 patients (4 men, 1 woman; median [range] age, 70 [56-77] years), 9 (40.9%) were positive for recurrent disease on HRCM and histopathologically confirmed, and 13 (59.1%) sites were negative on HRCM, but 3 of the 13 were positive for EMPD on histopathological examination. In general, HRCM had a sensitivity of 75% and a specificity of 100% in identifying recurrent or persistent EMPD. False-negative results were found in 2 patients and occurred at the margins of EMPD, close to previous biopsy sites. Creating video mosaics (or video mosaicking) seemed to improve the detection of EMPD. Conclusions and Relevance Handheld reflectance confocal microscopy is a useful auxiliary tool for diagnosing EMPD recurrences and can be used to guide scouting biopsies, thus reducing the number of biopsies needed to render a correct diagnosis.

Cutaneous malignancies are common malignancies worldwide, with rising incidence. Most skin cancers, including melanoma, can be cured if diagnosed correctly at an early stage. Thus, millions of biopsies are performed annually, posing a major economic burden. Non-invasive skin imaging techniques can aid in early diagnosis and save unnecessary benign biopsies. In this review article, we will discuss in vivo and ex vivo confocal microscopy (CM) techniques that are currently being utilized in dermatology clinics for skin cancer diagnosis. We will discuss their current applications and clinical impact. Additionally, we will provide a comprehensive review of the advances in the field of CM, including multi-modal approaches, the integration of fluorescent targeted dyes, and the role of artificial intelligence for improved diagnosis and management.

Background: Full-field optical coherence tomography (FFOCT) is a real-time imaging technique that rapidly generates images reminiscent of histology without any tissue processing, warranting its exploration for evaluation of ex vivo kidney tissue. Methods: Fresh tissue sections from tumor and adjacent nonneoplastic kidney (n = 25 nephrectomy specimens; clear cell renal cell carcinoma (CCRCC) = 12, papillary RCC (PRCC) = 4, chromophobe RCC (ChRCC) = 4, papillary urothelial carcinoma (PUC) = 1, angiomyolipoma (AML) = 2 and cystic nephroma = 2) were imaged with a commercial FFOCT device. Sections were submitted for routine histopathological diagnosis. Results: Glomeruli, tubules, interstitium, and blood vessels were identified in nonneoplastic tissue. In tumor sections, the normal architecture was completely replaced by either sheets of cells/trabeculae or papillary structures. The former pattern was seen predominantly in CCRCC/ChRCC and the latter in PRCC/PUC (as confirmed on H&E). Although the cellular details were not very prominent at this resolution, we could identify unique cytoplasmic signatures in some kidney tumors. For example, the hyper-intense punctate signal in the cytoplasm of CRCC represents glycogen/lipid, large cells with abundant hyper-intense cytoplasm representing histiocytes in PRCC, and signal-void large polygonal cell representing adipocytes in AML. According to a blinded analysis was performed by an uropathologist, all nonneoplastic tissues were differentiated from neoplastic tissues. Further, all benign tumors were called benign and malignant were called malignant. A diagnostic accuracy of 80% was obtained in subtyping the tumors. Conclusion: The ability of FFOCT to reliably differentiate nonneoplastic from neoplastic tissue and identify some tumor types makes it a valuable tool for rapid evaluation of ex vivo kidney tissue e.g. for intraoperative margin assessment and kidney biopsy adequacy. Recently, higher resolution images were achieved using an experimental FFOCT setup. This setup has the potential to further increase the diagnostic accuracy of FFOCT.