Reflectance confocal microscopy made easy: The 4 must-know key features for the diagnosis of melanoma and nonmelanoma skin cancers

Reflectance confocal microscopy in diagnosing basal cell carcinoma in the UK: a prospective observational single-centre trial

BACKGROUND

Previous work with reflectance confocal microscopy (RCM) has shown high sensitivity and specificity for basal cell carcinoma (BCC); however, to date, there have been few studies in UK cohorts.

OBJECTIVES

To assess the potential of RCM to accurately diagnose BCC in a private UK secondary care, single-clinician setting, and to investigate the potential of RCM as a routine diagnostic procedure.

METHODS

In total, 522 lesions where BCC featured in the differential diagnosis after clinical examination were prospectively recruited; 78 lesions were subsequently excluded. We used an arm-mounted confocal microscope unless access to the lesion was awkward and required a handheld probe to be used. The likelihood of BCC was scored for each modality (clinical examination, dermoscopy and RCM), with each diagnosis building on the last. Histology was assessed by a single blinded histopathologist. The study was registered with ClinicalTrials.gov (NCT03509415).

RESULTS

The analysis included 444 lesions (327 BCCs) from 326 patients. The median maximum lesion diameter was 6 mm. The sensitivity and specificity for BCC were 69.4% [95% confidence interval (CI) 64.1-74.4] and 53.0% (95% CI 43.6-62.3), respectively, for clinical examination alone; 91.8% (95% CI 88.3-94.5) and 41.0% (95% CI 32.0-50.5), respectively, for clinical examination plus dermoscopy; and 98.8% (95% CI 96.9-99.7) and 85.5% (95% CI 77.8-91.3), respectively, for clinical examination plus dermoscopy plus RCM. For RCM, the positive predictive value in diagnosing BCC was 95.0% (95% CI 92.1-97.1) and the negative predictive value was 96.2% (95% CI 90.4-98.9). The area under the curve increased from 0.61 to 0.66 to 0.92 as the respective modalities were added.

CONCLUSIONS

This study demonstrates that RCM can reliably and quickly diagnose BCC, and that the addition of RCM to dermoscopy permits higher diagnostic accuracy for BCC in the UK. The specificity and sensitivity of the RCM diagnosis did not alter significantly with experience, reflecting the ease and speed of acquiring the skills required to use this modality.

Reflectance confocal microscopy to diagnose malignant melanoma and lentigo maligna in the UK: a single-centre prospective observational trial

BACKGROUND

Previous work with reflectance confocal microscopy (RCM) has shown high sensitivity and specificity for malignant melanoma (MM); however, to date, there have been no studies with a UK cohort.

OBJECTIVES

To use RCM prospectively to accurately diagnose MM and lentigo maligna (LM) in a private UK secondary care, single-clinician setting; and to assess the potential of RCM to be used as a routine screening procedure.

METHODS

In total, 597 patients with a differential clinical diagnosis of MM or LM were consecutively recruited. A sequential record was made of the clinical, dermoscopy and RCM findings by a single dermatologist prior to biopsy. Imaging was done with an arm-mounted confocal microscope unless there was restricted access to a lesion that required a handheld probe. The likelihood of MM was scored for each diagnostic modality, with each diagnosis building on the last. Histology was assessed by a single blinded histopathologist. The trial was registered with ClinicalTrials.gov (NCT03508297).

RESULTS

Altogether, 733 lesions were included in the analysis, including 86 MM and LM (median diameter 7.0 mm). The benign-to-malignant ratio was 3 : 1 (nonmelanocytic malignancies included) and 8.3 : 1 for MM and LM only. The sensitivity and specificity for MM and LM, respectively, was 62.8% [95% confidence interval (CI) 51.7-73.0] and 63.1% (95% CI 59.3-66.8) for clinical examination; 91.9% (95% CI 84.0-96.7) and 42.0% (95% CI 38.1-45.9), respectively, for dermoscopy; and 94.2% (95% CI 87.0-98.1) and 83.0% (95% CI 79.9-85.8), respectively, for RCM. The positive predictive value of RCM in diagnosing MM and LM was 42.4% (95% CI 38.1-46.8) and the negative predictive value was 99.1% (95% CI 97.9-99.6).

CONCLUSIONS

This study demonstrates that RCM can reliably diagnose MM and is fast enough to be integrated into UK pigmented lesion clinics by dermatologists trained in RCM. The number needed to treat decreased from 3.86 with clinical examination to 2.96 with dermoscopy to 1.30 with RCM.

Differential Expression Analysis of Cutaneous Squamous Cell Carcinoma and Basal Cell Carcinoma Proteomic Profiles Sampled with Electroporation-Based Biopsy

Clinical misdiagnosis between cutaneous squamous cell carcinoma (cSCC) and basal cell carcinoma (BCC) affects treatment plans. We report a tissue sampling approach with molecular biopsy using electroporation. This method, coined electroporation-based biopsy (e-biopsy), enables nondestructive nonthermal permeabilization of cells in the skin for vacuum-assisted extraction of biomolecules. We used e-biopsy for ex vivo proteome extraction from 3 locations per patient in 21 cSCC, 20 BCC, and 7 actinic keratosis human skin samples. Using liquid chromatography with tandem mass spectrometry, we identified 5966 proteins observed with nonzero intensity in at least 1 sample. The intrapatient Pearson correlation of 0.888 ± 0.065 for patients with BCC, 0.858 ± 0.077 for patients with cSCC, and 0.876 ± 0.116 for those with solar actinic keratosis indicates high consistency of the e-biopsy sampling. The mass spectra presented significantly different proteome profiles for cSCC, BCC, and solar actinic keratosis, with several hundreds of proteins differentially expressed. Notably, our study showed that proteomes sampled with e-biopsy from cSCC and BCC lesions are different and that proteins of CRNN, SULT1E1, and ITPK1 genes are significantly overexpressed in BCC in comparison with those in cSCC. Our results provide evidence that the e-biopsy approach could potentially be used as a tool to support cutaneous lesions classification with molecular pathology.

Basosquamous carcinoma: Comprehensive epidemiological, clinical, dermoscopic, and confocal features from a single center institution

BACKGROUND

Basosquamous carcinoma (BSC) is a rare and aggressive nonmelanoma skin cancer (NMSC) that exhibits features of both BCC and squamous cell carcinoma (SCC). The gold standard for diagnosis is histopathological examination. BSC is often challenging to diagnose and manage due to its mixed histological features and potential for aggressive behavior AIM: To identify specific features aiding clinicians in differentiating BSCs using non-invasive diagnostic techniques.

METHODS

We conducted a retrospective descriptive, monocentric study of the epidemiological clinical, dermoscopic, and reflectance confocal microscopy (RCM) features of histopathologically proven BSCs diagnosed between 2010 and 2023. A total of 192 cases were selected.

RESULTS

The study population consisted of 17 men (60.9%). Total 95.8% of patients at the time of diagnosis were ≥50 years. BSC occurred in the head and neck area in 124 cases (63.1%) of which 65 (33.9%) were in the H-zone. For 47.4% of patients, BSC presented as a macule with undefined clinical margins (43.3%). Dermoscopic images were available for 98 cases: the most common parameter was the presence of whitish structureless areas (59 [60.2%]), keratin masses (58 [59.2%]), superficial scales, and ulceration or blood crusts (49 [50%] both). Vessels pattern analysis revealed hairpin vessels (exclusively) and linear irregular vessels as the most frequent (55 [56.1%] both). RCM examination was performed in 21 cases which revealed specific SCC features such as solar elastosis (19 [90.5%]), atypical honeycomb pattern (17 [89%]), proliferation of atypical keratinocytes (16 [80%]) combined with BCC' ones as bright tumor islands (12 [57.8%]), and cleft-like dark spaces (11 [53.4%]).

DISCUSSION

Our study reflects the largest cohort of BSCs from a single institution. We described an incidence rate of 4.7%, higher than reported in the Literature, with the involvement of patients ≥50years in almost 96% of cases and an overall male predominance. At clinical examination, BSC was described as a hyperkeratotic macule with undefined clinical margins with one or more dermoscopic SCC' features, whereas the presence of typical BCC aspects was observed in less than 10% of cases, differently from what was previously reported. At RCM analysis, BSCs presented with an atypical honeycomb pattern with proliferation of atypical keratinocytes, hyperkeratosis, and in nearly 55% of patients, bright tumor islands with cleft-like dark spaces.

CONCLUSION

The distinctive dermoscopic patterns, along with the RCM features aid in the differentiation of BSCs from other NMSCs.

Reflectance confocal microscopy as noninvasive tool for monitoring tirbanibulin efficacy in actinic keratosis

Actinic keratosis (AK) is a common precancerous condition found on sun-damaged skin. Tirbanibulin 1 % ointment has been approved for the topical treatment of non-hyperkeratotic facial and scalp Olsen grade I AKs over a contiguous area of 25 cm2 with a daily application for 5 consecutive days. Our aim was to investigate the use of in vivo RCM in the assessment of the response of AKs treated with tirbanibulin, as it has never been described in the published Literature. A total of 10 AKs in 10 consecutive outpatients were enrolled in the present study in May 2023. The follow-up visit was scheduled after 30 days from last application of tirbanibulin ointment. At follow-up visit, a complete response was described by clinical, dermoscopic and in vivo RCM examination in 10 out of 10 lesions, with a recovery of stratum corneum, decrease in atypical honeycomb pattern and changes in dermal collagen. All patients were followed up for at least 8 months and further recurrences were not registered. Based on our experience, we confirm the efficacy and safety of tirbanibulin in treating AKs and the usefulness of RCM in vivo examination for the therapeutic monitoring of such lesions, even in a very early stage.

Dermatoscopy and reflectance confocal microscopy for basal cell carcinoma diagnosis and diagnosis prediction score: A prospective and multicenter study on 1005 lesions

BACKGROUND

Basal cell carcinoma (BCC) is usually diagnosed by clinical and dermatoscopy examination, but diagnostic accuracy may be suboptimal. Reflectance confocal microscopy (RCM) imaging increases skin cancer diagnostic accuracy.

OBJECTIVE

To evaluate additional benefit in diagnostic accuracy of handheld RCM in a prospective controlled clinical setting.

METHODS

A prospective, multicenter study in 3 skin cancer reference centers in Italy enrolling consecutive lesions with clinical-dermatoscopic suspicion of BCC (ClinicalTrials.gov: NCT04789421).

RESULTS

A total of 1005 lesions were included, of which 474 histopathologically confirmed versus 531 diagnosed by clinical-dermatoscopic-RCM correlation, confirmed with 2 years of follow-up. Specifically, 740 were confirmed BCCs. Sensitivity and specificity for dermatoscopy alone was 93.2% (95% CI, 91.2-94.9) and 51.7% (95% CI, 45.5-57.9); positive predictive value was 84.4 (95% CI, 81.7-86.8) and negative predictive value 73.3 (95% CI, 66.3-79.5). Adjunctive RCM reported higher rates: 97.8 (95% CI, 96.5-98.8) sensitivity and 86.8 (95% CI, 82.1-90.6) specificity, with positive predictive value of 95.4 (95% CI, 93.6-96.8) and negative predictive value 93.5 (95% CI, 89.7-96.2).

LIMITATIONS

Study conducted in a single country.

CONCLUSIONS

Adjunctive handheld RCM assessment of lesions clinically suspicious for BCC permits higher diagnostic accuracy with minimal false negative lesions.

[Translated article] Reflectance Confocal Microscopy Terminology in Spanish: A Delphi Consensus Study

The terminology used to describe reflectance confocal microscopy (RCM) findings in both melanocytic and nonmelanocytic lesions has been standardized in English. We convened a panel of Spanish-speaking RCM experts and used the Delphi method to seek consensus on which Spanish terms best describe RCM findings in this setting. The experts agreed on 52 terms: 28 for melanocytic lesions and 24 for nonmelanocytic lesions. The resulting terminology will facilitate homogenization, leading to a better understanding of structures, more standardized descriptions in clinical registries, and easier interpretation of clinical reports exchanged between dermatologists.

International expert recommendations on image acquisition for in vivo reflectance confocal microscopy of cutaneous tumors

BACKGROUND

No international recommendations exist for a minimum imaging requirement per lesion using reflectance confocal microscopy (RCM). This may be beneficial given the increasing use of remote RCM interpretation internationally.

OBJECTIVE

To develop international expert recommendations for image acquisition using tissue-coupled RCM for diagnosis of cutaneous tumors.

METHODS

Using a modified Delphi approach, a core group developed the scope and drafted initial recommendations before circulation to a larger group, the Cutaneous Imaging Expert Resource Group of the American Academy of Dermatology. Each review round consisted of a period of open comment, followed by revisions.

RESULTS

The recommendations were developed after 5 alternating rounds of review among the core group and the Cutaneous Imaging Expert Resource Group. These were divided into subsections of imaging personnel, recommended lesion criteria, clinical and lesion information to be provided, lesion preparation, image acquisition, mosaic cube settings, and additional captures based on lesion characteristics and suspected diagnosis.

LIMITATIONS

The current recommendations are limited to tissue-coupled RCM for diagnosis of cutaneous tumors. It is one component of the larger picture of quality assurance and will require ongoing review.

CONCLUSIONS

These recommendations serve as a resource to facilitate quality assurance, economical use of time, accurate diagnosis, and international collaboration.

Reflectance Confocal Microscopy Terminology in Spanish: A Delphi Consensus Study

The terminology used to describe reflectance confocal microscopy (RCM) findings in both melanocytic and nonmelanocytic lesions has been standardized in English. We convened a panel of Spanish-speaking RCM experts and used the Delphi method to seek consensus on which Spanish terms best describe RCM findings in this setting. The experts agreed on 52 terms: 28 for melanocytic lesions and 24 for nonmelanocytic lesions. The resulting terminology will facilitate homogenization, leading to a better understanding of structures, more standardized descriptions in clinical registries, and easier interpretation of clinical reports exchanged between dermatologists.

Melanoma clinicopathological groups characterized and compared with dermoscopy and reflectance confocal microscopy

BACKGROUND

Dermoscopic and reflectance confocal microscopy (RCM) correlations between morphologic groups of melanoma have not yet been described.

OBJECTIVE

Describe and compare dermoscopic and RCM features of cutaneous melanomas with histopathological confirmation.

METHODS

Single center, retrospective analysis of consecutive melanomas evaluated with RCM (2015-2019). Lesions were clinically classified as typical, nevus-like, amelanotic/nonmelanoma skin cancer (NMSC)-like, seborrheic keratosis (SK)-like and lentigo/lentigo maligna (LM)-like. Presence or absence of common facial and nonfacial melanoma dermoscopic and RCM patterns were recorded. Clusters were compared with typical lesions by multivariate logistic regression.

RESULTS

Among 583 melanoma lesions, significant differences between clusters were evident (compared to typical lesions). Observation of dermoscopic features (>50% of lesions) in amelanotic/NMSC-like lesions consistently displayed 3 patterns (atypical network, atypical vascular pattern + regression structures), and nevus-like and SK-like lesions and lentigo/LM-like lesions consistently displayed 2 patterns (atypical network + regression structures, and nonevident follicles + heavy pigmentation intensity). Differences were less evident with RCM, as almost all lesions were consistent with melanoma diagnosis.

LIMITATIONS

Small SK-like lesions sample, single RCM analyses (no reproduction of outcome).

CONCLUSION

RCM has the potential to augment our ability to consistently and accurately diagnose melanoma independently of clinical and dermoscopic features.

Concordance between reflectance confocal microscopy and histopathology for the diagnosis of acral lentiginous melanoma

BACKGROUND

Acral lentiginous melanoma (ALM) is a highly malignant and invasive type of melanoma with unique locations of onset. Its incidence is increasing and early diagnosis is challenging. Reflectance confocal microscopy (RCM) is a non-invasive technique that provides an accurate image of tissue pathology. There are few reports on the use of RCM for the assessment of ALM.

MATERIALS AND METHODS

In this retrospective study, data from 31 patients with a clinical diagnosis of ALM were collected. RCM image features were compared with histopathological findings to determine the concordance between the two methods. The sensitivity, specificity, positive predictive value, and negative predictive value of RCM for the diagnosis of ALM were evaluated.

RESULTS

RCM and histopathology findings were concordant in 29 of 31 patients (93.5%). There were no false-negative results, although there were two false positives in RCM diagnosis. The sensitivity of RCM for diagnosing ALM was 100%, specificity was 50%, positive predictive value was 93.1%, and negative predictive value was 100%.

CONCLUSIONS

RCM showed substantial concordance with histopathology in the diagnosis of ALM. It is a reliable and valuable non-invasive diagnostic tool that holds promise for the early diagnosis of ALM.

[Non-invasive automated methods for the diagnosis of periorbital skin tumors]

Malignant skin tumors are the most common type of cancer in both Russia and globally. Malignant skin tumors located in the periorbital region, particularly basal cell carcinoma, pose a significant threat to the visual organ due to the high risk of local invasion, highlighting the need for early diagnosis and timely treatment. This review discusses the main methods of non-invasive instrumental diagnosis of skin tumors in the periorbital region. Key stages in the development of these methods are briefly outlined, and their most significant advantages and disadvantages are noted. The article also considers the automation of diagnostic studies, and potential challenges with its practical implementation.

The role of in vivo reflectance confocal microscopy for the management of acne: A systematic review

Acne diagnosis, severity assessment and treatment follow-up rely primarily on clinical examination. In vivo reflectance confocal microscopy (RCM) provides non-invasively, real-time images of skin lesions with a level of detail close to histopathology. This systematic literature review aims to provide an overview of RCM utility in acne and a summary of specific features with clinical application that may increase objectivity in evaluating this condition. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for reporting our results. We systematically searched three databases: PubMed, Clarivate and Google Scholar (January 2022). All included studies used RCM to investigate acne in human patients and reported the investigated skin area and type (acne lesions or clinically uninvolved skin), the substance used in the case of treatment. Our search identified 2184 records in the three databases investigated. After duplicate removal, 1608 records were screened, 35 were selected for full-text assessment, and 14 were included in this review. We used the QUADAS-2 tool to evaluate the risk of bias and applicability concerns. RCM was selected as the index test and clinical examination as the reference standard. The total number of patients from all studies was 291, with 216 acne patients and 60 healthy participants aged between 13 and 45 years. The 14 considered studies analysed 456 follicles from healthy participants, 1445 follicles from uninvolved skin in acne patients and 1472 acne lesions. Consistent RCM findings concerning follicles of acne patients reported across studies were increased follicular infundibulum size, thick, bright border, intrafollicular content and inflammation. Our analysis indicates that RCM is a promising tool for acne evaluation. Nevertheless, standardization, a unified terminology, consistent research methods and unitary reporting of RCM findings are necessary. PROSPERO registration number CRD42021266547.

High Frequency Ultrasound of Basal Cell Carcinomas: Ultrasonographic Features and Histological Subtypes, a Retrospective Study of 100 Tumors

(1) Background: 22 MHz high frequency ultrasound (HFUS) is a non-invasive imaging technique that gives information on depth, length, volume and shape of skin tumors. (2) Methods: We reviewed the clinical, ultrasound, and histological records of 54 patients with 100 histologically confirmed basal cell carcinoma (BCC) tumors with the use of HFUS. (3) Results: Most infiltrative tumors (n = 16/21, 76.2%) were irregular shaped, followed by five (23.8%) being round shaped; most superficial tumors (n = 25/29, 86.2%) were ribbon shaped, followed by four (13.8%) being round shaped; most nodular tumors (n = 26/33, 78.8%) were round shaped, followed by seven (21.2%) that were irregular shaped; and, lastly, all microdular tumors (n = 2/2, 100%) were round shaped. Strong evidence of association (p = 0.000) was observed between the histological subtype and tumor shape as seen using the HFUS. No evidence of association was found between the histological subtype and tumor margin (p > 0.005). Cohen's Kappa statistic to assess the agreement between BCC subtypes evaluated by histological examination and U/S appearance was calculated equal to 0.8251 (almost perfect agreement). (4) Conclusions: HFUS appears to be a reliable technique for the pre-operative evaluation of BCCs, assisting physicians to decide on the optimal therapeutic approach.

Confocal Microscopy for Diagnosis and Management of Cutaneous Malignancies: Clinical Impacts and Innovation

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.

Enhancing Skin Cancer Immunotheranostics and Precision Medicine through Functionalized Nanomodulators and Nanosensors: Recent Development and Prospects

Skin cancers, especially melanomas, present a formidable diagnostic and therapeutic challenge to the scientific community. Currently, the incidence of melanomas shows a high increase worldwide. Traditional therapeutics are limited to stalling or reversing malignant proliferation, increased metastasis, or rapid recurrence. Nonetheless, the advent of immunotherapy has led to a paradigm shift in treating skin cancers. Many state-of-art immunotherapeutic techniques, namely, active vaccination, chimeric antigen receptors, adoptive T-cell transfer, and immune checkpoint blockers, have achieved a considerable increase in survival rates. Despite its promising outcomes, current immunotherapy is still limited in its efficacy. Newer modalities are now being explored, and significant progress is made by integrating cancer immunotherapy with modular nanotechnology platforms to enhance its therapeutic efficacy and diagnostics. Research on targeting skin cancers with nanomaterial-based techniques has been much more recent than other cancers. Current investigations using nanomaterial-mediated targeting of nonmelanoma and melanoma cancers are directed at augmenting drug delivery and immunomodulation of skin cancers to induce a robust anticancer response and minimize toxic effects. Many novel nanomaterial formulations are being discovered, and clinical trials are underway to explore their efficacy in targeting skin cancers through functionalization or drug encapsulation. The focus of this review rivets on theranostic nanomaterials that can modulate immune mechanisms toward protective, therapeutic, or diagnostic approaches for skin cancers. The recent breakthroughs in nanomaterial-based immunotherapeutic modulation of skin cancer types and diagnostic potentials in personalized immunotherapies are discussed.

Reflectance confocal microscopy of facial neoplasms: Follicular involvement as a clue to diagnosis

BACKGROUND

Facial skin is characterized by high density of follicles. Facial neoplasms may present overlapping clinical and dermoscopic findings. Our goal was to evaluate and compare, via reflectance confocal microscopy (RCM), follicular involvement in facial neoplasms.

METHODS

We retrospectively searched our image database, between January 2008 and December 2020, for all facial lesions with (1) a standardized set of clinical, dermoscopic, and RCM images, and (2) a biopsy-proven diagnosis of lentigo maligna/lentigo maligna melanoma (LM/LMM, n = 39), basal cell carcinoma (BCC, n = 51), squamous cell carcinoma in situ (SCCIS, n = 5), actinic keratosis (AK, n = 11), and lichen-planus-like keratosis (LPLK, n = 18). Two readers jointly evaluated the RCM images for a set of predefined features of follicular involvement.

RESULTS

Diffuse obliteration of follicles was frequent in BCC (88%), while follicular infiltration by refractile dendritic cells and/or by bright round nucleated cells was common in melanoma (90% and 44%, respectively). Extension of atypical keratinocytes down follicles was more prominent among SCCIS than AK (80% vs. 45%, p = 0.01). In most LPLK (89%), there was follicular sparing.

CONCLUSIONS

Evaluation of RCM criteria centering on the follicles can be useful in the differential diagnosis between common facial neoplasms.

Automating reflectance confocal microscopy image analysis for dermatological research: a review

SIGNIFICANCE

Reflectance confocal microscopy (RCM) is a noninvasive, in vivo technology that offers near histopathological resolution at the cellular level. It is useful in the study of phenomena for which obtaining a biopsy is impractical or would cause unnecessary tissue damage and trauma to the patient.

AIM

This review covers the use of RCM in the study of skin and the use of machine learning to automate information extraction. It has two goals: (1) an overview of information provided by RCM on skin structure and how it changes over time in response to stimuli and in disease and (2) an overview of machine learning approaches developed to automate the extraction of key morphological features from RCM images.

APPROACH

A PubMed search was conducted with additional literature obtained from references lists.

RESULTS

The application of RCM as an in vivo tool in dermatological research and the biologically relevant information derived from it are presented. Algorithms for image classification to epidermal layers, delineation of the dermal-epidermal junction, classification of skin lesions, and demarcation of individual cells within an image, all important factors in the makeup of the skin barrier, were reviewed. Application of image analysis methods in RCM is hindered by low image quality due to noise and/or poor contrast. Use of supervised machine learning is limited by time-consuming manual labeling of RCM images.

CONCLUSIONS

RCM has great potential in the study of skin structures. The use of artificial intelligence could enable an easier, more reproducible, precise, and rigorous study of RCM images for the understanding of skin structures, skin barrier, and skin inflammation and lesions. Although several attempts have been made, further work is still needed to provide a definite gold standard and overcome issues related to image quality, limited labeled datasets, and lack of phenotype variability in available databases.

Hotspot analysis by confocal microscopy can help to differentiate challenging melanocytic skin lesions

Some melanocytic lesions do not present enough clinical and dermoscopic features to allow ruling out a possible melanoma diagnosis. These “doubtful melanocytic lesions” pose a very common and challenging scenario in clinical practice and were selected at this study for reflectance confocal microscopy evaluation and subsequent surgical excision for histopathological diagnosis. The study included 110 lesions and three confocal features were statistically able to distinguish benign melanocytic lesions from melanomas: “peripheral hotspot at dermo-epidermal junction”, “nucleated roundish cells at the dermo-epidermal junction” and “sheet of cells”. The finding of a peripheral hotspot (atypical cells in 1mm²) at the DEJ is highlighted because has not been previously reported in the literature as a confocal feature related to melanomas.

Biopsy-free in vivo virtual histology of skin using deep learning

An invasive biopsy followed by histological staining is the benchmark for pathological diagnosis of skin tumors. The process is cumbersome and time-consuming, often leading to unnecessary biopsies and scars. Emerging noninvasive optical technologies such as reflectance confocal microscopy (RCM) can provide label-free, cellular-level resolution, in vivo images of skin without performing a biopsy. Although RCM is a useful diagnostic tool, it requires specialized training because the acquired images are grayscale, lack nuclear features, and are difficult to correlate with tissue pathology. Here, we present a deep learning-based framework that uses a convolutional neural network to rapidly transform in vivo RCM images of unstained skin into virtually-stained hematoxylin and eosin-like images with microscopic resolution, enabling visualization of the epidermis, dermal-epidermal junction, and superficial dermis layers. The network was trained under an adversarial learning scheme, which takes ex vivo RCM images of excised unstained/label-free tissue as inputs and uses the microscopic images of the same tissue labeled with acetic acid nuclear contrast staining as the ground truth. We show that this trained neural network can be used to rapidly perform virtual histology of in vivo, label-free RCM images of normal skin structure, basal cell carcinoma, and melanocytic nevi with pigmented melanocytes, demonstrating similar histological features to traditional histology from the same excised tissue. This application of deep learning-based virtual staining to noninvasive imaging technologies may permit more rapid diagnoses of malignant skin neoplasms and reduce invasive skin biopsies.

Reflectance Confocal Microscopy of Aging Skin and Skin Cancer

Skin aging is a complex process that causes morphologic variations. Some of these variations have been hypothesized to be involved in skin cancer development. This paper reviews current knowledge of the features of aged skin as seen with reflectance confocal microscopy (RCM). Basic principles of the technique are described, and the RCM features of healthy skin and skin cancer are briefly discussed. Moreover, the RCM features at different layers of young and elderly skin are described, as are the variations that occur with passing years and in relation to sun exposure that contribute to photoaging and the development of skin cancer. RCM enables the noninvasive evaluation, at quasi-histologic resolution, of aging-related skin changes, some of which are shared with skin cancer; this ability helps avoid skin biopsy. Further research is needed to understand the relation between skin aging and skin cancer development.

Langerhans Cells as Morphologic Mimickers of Atypical Melanocytes on Reflectance Confocal Microscopy: A Case Report and Review of the Literature

Pagetoid spread of melanocytes in the epidermis is a common indicator of melanocytic atypia, both histopathologically and with reflectance confocal microscopy (RCM). Specifically on RCM, large, bright, atypical dendritic and/or roundish cells are characteristic of melanoma. However, intraepidermal Langerhans cells (ILC) create the potential for diagnostic ambiguity on RCM. We describe one case of a pigmented facial lesion that was initially diagnosed as lentigo maligna (LM) due to numerous atypical perifollicular dendritic cells on RCM. Additionally, we present the findings of a literature review for similar reported cases conducted by searching the following terms on PubMed: reflectance confocal microscopy, RCM, lentigo maligna, melanoma, Langerhans cells, dendritic cells, and atypical cells. In our case, the lesion was determined to be a solar lentigo on histopathology. Immunohistochemistry (IHC) with CD1a identified the atypical-appearing cells as ILC, as it did in 54 reported cases of benign lesions (benign melanocytic nevus, Sutton/halo nevus, labial melanotic macule, and solar lentigo) misdiagnosed as malignant on RCM (melanoma, lip melanoma, lentigo maligna, and LM melanoma). According to our case and the literature, both ILC and atypical melanocytes can present with atypical-appearing dendritic and/or roundish cells under RCM. Currently, there is no method to distinguish the two without IHC. Therefore, the presence of pagetoid cells should continue to alert the confocalist of a potential neoplastic process, prompting biopsy, histopathologic diagnosis, and IHC differentiation.

Tips for difficult to diagnose hypomelanotic melanomas on reflectance confocal microscopy

Amelanotic/hypomelanotic melanoma (AHM) represents a clinical diagnostic challenge. Dermoscopy improves AHM diagnosis thanks to visualization of little pigment and vascular pattern. Reflectance confocal microscopy (RCM) increases further the diagnostic accuracy of AHM but few and small studies have described in detail RCM features of AHM. We evaluated dermoscopic and RCM features of nine cases of difficult to diagnose hypomelanotic melanomas (HMs) to find clues for their diagnosis. The RCM score was suggestive of melanoma in all cases. The major criteria of nonedged papillae and/or cytological atypia at the dermo-epidermal junction were seen in all cases. Among the minor criteria, roundish pagetoid cells, including hyporeflective pagetoid cells, were found in four out of nine lesions. Dermoscopically, four out of nine HMs did not show prevalent suspicious criteria while revealing suspicious RCM features that were visible only after careful RCM examination by zooming mosaic images. RCM can improve HM diagnostic accuracy but only after extensive evaluation of images. Atypical cells were less reflective and the architectural irregularity was less visible than in pigmented melanoma and zooming was needed to identify both features.

Clinical Applications of In Vivo and Ex Vivo Confocal Microscopy

Confocal laser scanning microscopy (CLSM) has been introduced in clinical settings as a tool enabling a quasi-histologic view of a given tissue, without performing a biopsy. It has been applied to many fields of medicine mainly to the skin and to the analysis of skin cancers for both in vivo and ex vivo CLSM. In vivo CLSM involves reflectance mode, which is based on refractive index of cell structures serving as endogenous chromophores, reaching a depth of exploration of 200 μm. It has been proven to increase the diagnostic accuracy of skin cancers, both melanoma and non-melanoma. While histopathologic examination is the gold standard for diagnosis, in vivo CLSM alone and in addition to dermoscopy, contributes to the reduction of the number of excised lesions to exclude a melanoma, and to improve margin recognition in lentigo maligna, enabling tissue sparing for excisions. Ex vivo CLSM can be performed in reflectance and fluorescent mode. Fluorescence confocal microscopy is applied for “real-time” pathological examination of freshly excised specimens for diagnostic purposes and for the evaluation of margin clearance after excision in Mohs surgery. Further prospective interventional studies using CLSM might contribute to increase the knowledge about its application, reproducing real-life settings.

Real-Time Confocal Imaging for Hidradenitis Suppurativa: Description of Morphological Aspects and Focus on the Role of Follicular Ostia

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic, recurrent, inflammatory skin disease involving the follicular unit. Growing evidence suggests a crucial role of hyperkeratosis, infundibular plugging and perifolliculitis in its pathogenesis.

OBJECTIVES

To characterize the microscopic morphology of open comedos using in vivo reflectance confocal microscopy (RCM) and define alterations occurring in HS normal-appearing perilesional skin compared to healthy skin of a control group, discussing therefore microscopic differences.

MATERIALS AND METHODS

Twenty patients (11 males, 9 females; aged 19-51 years) affected by HS were recruited. RCM was performed on open comedos of axillary/inguinal regions and on normal-appearing skin areas distant at least 1.5 cm from HS lesions. Ten healthy individuals (6 males, 4 females) were included as control group.

RESULTS

RCM aspects of 78 open comedos were explored, observing circular/ovoidal structures disclosing a hyperrefractive amorphous material (72/78, 92.3%) within the infundibular cavity surrounded with a bright (51/78, 65.4%) and regular (52/78, 66.2%) border. Follicular ostia of HS perilesional skin (n = 541) compared to follicular ostia of a control group (n = 321) were characterized by a larger infundibular diameter (183.4 vs. 85.8 µm) and diverged in terms of material collected inside infundibula (44.5 vs. 21%) and keratinization of the border (47.6 vs. 25.5%).

CONCLUSION

In vivo characterization of open comedos and the recognition of microscopic subclinical alterations of HS normal-appearing skin, compared to healthy skin, could add further insights into the definition of biological events leading to HS manifestations, including the dysregulated process of keratinization.

Dark pigmented lesions: Diagnostic accuracy of dermoscopy and reflectance confocal microscopy in a tertiary referral center for skin cancer diagnosis

BACKGROUND

There is lack of studies on the diagnostic accuracy of dermoscopy and reflectance confocal microscopy (RCM) for dark pigmented lesions.

OBJECTIVE

To assess the diagnostic accuracy of dermoscopy plus confocal microscopy for melanoma diagnosis of dark pigmented lesions in real life.

METHODS

Prospective analysis of difficult dark lesions with clinical/dermoscopic suspicion of melanoma referred for RCM for further analysis. The outcome could be excision or dermoscopic digital follow-up.

RESULTS

We included 370 clinically dark lesions from 350 patients (median age, 45 y). Because of the clinical/dermoscopic/RCM approach, we saved 129 of 213 unnecessary biopsies (specificity of 60.6%), with a sensitivity of 98.1% (154/157). The number needed to excise with the addition of RCM was 1.5 for melanoma diagnosis.

LIMITATIONS

Single institution based; Italian population only.

CONCLUSIONS

This study showed that RCM coupled with dermoscopy increases the specificity for diagnosing melanoma, and it helps correctly identify benign lesions. Our findings provide the basis for subsequent prospective studies on melanocytic neoplasms belonging to patients in different countries.

Reflectance confocal microscopy: Diagnostic criteria of common benign and malignant neoplasms, dermoscopic and histopathologic correlates of key confocal criteria, and diagnostic algorithms

Reflectance confocal microscopy (RCM) is a high-resolution, noninvasive tool that is currently approved by the US Food and Drug Administration for obtaining and interpreting images of the skin and cutaneous neoplasms with the goal of decreasing unnecessary biopsy procedures in patients with benign lesions. The second article in this continuing medical education series focuses on identifying key criteria for the diagnosis of common skin cancers-melanoma, basal cell carcinoma, and squamous cell carcinoma. We contrast these findings with RCM features of common benign lesions-melanocytic nevi, solar lentigo, seborrheic keratosis, lichen planus-like keratosis, and sebaceous hyperplasia. We also correlate the dermoscopic and histopathologic findings with the RCM features.

Reflectance confocal microscopy: Principles, basic terminology, clinical indications, limitations, and practical considerations

Reflectance confocal microscopy (RCM) is a noninvasive imaging tool used for in vivo visualization of the skin. It has been extensively studied for use in the evaluation of equivocal cutaneous neoplasms to decrease the number of biopsy procedures in patients with benign lesions. Furthermore, its applications are broadening to include presurgical cancer margin mapping, tumor recurrence surveillance, monitoring of ablative and noninvasive therapies, and stratification of inflammatory disorders. With the approval of category I Current Procedural Terminology reimbursement codes for RCM image acquisition and interpretation, use of this technology has been increasingly adopted by dermatologists. The first article in this 2-part continuing medical education series highlights basic terminology, principles, clinical applications, limitations, and practical considerations in the clinical use of RCM technology.

Reflectance confocal microscopy terminology glossary for melanocytic skin lesions: A systematic review

BACKGROUND

There is lack of uniformity in the reflectance confocal microscopy (RCM) terminology for melanocytic lesions.

OBJECTIVE

To review published RCM terms for melanocytic lesions and identify redundant, synonymous terms.

METHODS

A systematic review of original research articles adhering to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines was conducted until August 15, 2018. Two investigators gathered all published RCM terms used to describe melanoma and melanocytic nevi. Synonymous terms were grouped based on similarity in definition and in histopathologic correlation.

RESULTS

Out of 156 full-text screened articles, 59 studies met the inclusion criteria. We identified 209 terms; 191 (91.4%) corresponding to high-magnification/cellular-level terms and 18 (8.6%) corresponding to low-magnification/architectural patterns terms. The overall average use frequency of RCM terms was 3.1 times (range, 1-31). By grouping of individual RCM terms based on likely synonymous definitions and by eliminating terms lacking clear definition, the total number of RCM terms could be potentially reduced from 209 to 40 terms (80.8% reduction).

LIMITATIONS

Non-English and non-peer-reviewed articles were excluded.

CONCLUSIONS

This systematic review of published RCM terms identified significant terminology redundancy. It provides the basis for subsequent terminology consensus on melanocytic neoplasms.