Line-field confocal optical coherence tomography in melanocytic and non-melanocytic skin tumors.

INTRODUCTION: Line-field confocal optical coherence tomography (LC-OCT) is a recently introduced, non-invasive skin imaging technique combining the technical advantages of reflectance confocal microscopy and conventional OCT in terms of isotropic resolution and in-tissue penetration. Several studies have been published so far about the use of LC-OCT in melanocytic and non-melanocytic skin tumors. The aim of this review was to summarize the currently available data on the use of LC-OCT for benign and malignant melanocytic and non-melanocytic skin tumors. EVIDENCE ACQUISITION: We searched scientific databases for any literature published up to 30th April 2023 and concerning the use of LC-OCT for melanocytic and non-melanocytic skin tumors. Identified papers were evaluated, and relevant information was extracted. EVIDENCE SYNTHESIS: A total of 29 studies were found including original articles, short reports, and letters to the Editor: 6 applied to melanocytic skin tumors, 22 to non-melanocytic skin tumors and 1 to both. The use of LC-OCT increased the diagnostic accuracy for melanocytic and non-melanocytic skin lesions. The highest diagnostic performance was found for basal cell carcinoma (BCC), but significant improvements in the diagnostic accuracy were also detected for the differentiation of actinic keratosis (AK) from squamous cell carcinoma (SCC) and of melanoma from nevi. The LC-OCT features of other skin tumors were also described and successfully correlated with histopathology. CONCLUSIONS: LC-OCT proved to increase the diagnostic accuracy for melanocytic and non-melanocytic skin lesions, thanks to the combination of high resolution/penetration, 3D reconstructions, and integrated dermoscopy. Although BCC seems the most suitable tumors for LC-OCT examination, the device is extremely performant for the differentiation of AK from SCC and the discrimination of melanoma from nevi as well. Additional studies on diagnostic performance and new investigations about the presurgical assessment of tumor margins with LC-OCT and its association with human and artificial intelligence algorithms are in progress.

Role of ultra-high-frequency ultrasound in the diagnosis and management of basal cell carcinoma: pilot study based on 117 cases.

BACKGROUND: Ultrasound imaging has recently benefited from the introduction of a new 70 MHz transducer able to provide high-resolution images, i.e. ultra-high-frequency ultrasound (UHFUS). AIM: To study the morphological features of basal cell carcinomas (BCCs) and measure BCC thickness by means of UHFUS examination. METHODS: In this retrospective multicentric study, 171 consecutive patients underwent UHFUS examination between November 2018 and May 2019 for suspected BCC. Diagnosis was confirmed by histopathology. A series of morphological parameters including echogenicity, structure, borders, shape composition (presence of intralesional structures) were investigated along with objective measurements such as thickness (maximum distance between the surface of the epidermis and the deepest part of the tumour) and width. RESULTS: In total, 117 BCCs from 93 patients were examined, including superficial (n = 13; 11.1%), nodular (n = 64; 54.7%), infiltrative (n = 18; 15.4%), mixed subtypes (n = 20; 17.1%) and other subtypes (n = 2; 1.7%). The most frequently observed UHFUS parameters included: hypoechoic signal (n = 80; 68.4%, P < 0.001), homogeneous structure (n = 76, 65.0%, P = 0.01), well-defined borders (n = 77, 65.8%, P < 0.001) and elongated shape (n = 71, 60.7%, P < 0.001). An excellent correlation was found between the BCC thickness measured by UHFUS and the value estimated by histology (interclass correlation ≥ 0.80). CONCLUSION: UHFUS is a new rapid and easy noninvasive skin imaging technique able to provide data on the dimensions and morphology of BCCs in real time and at the bedside. These characteristics mean UHFUS has a number of possible applications, ranging from presurgical mapping to the detection of disease recurrence and treatment monitoring.

Morphological evaluation of melanocytic lesions with three-dimensional line-field confocal optical coherence tomography: correlation with histopathology and reflectance confocal microscopy. A pilot study.

BACKGROUND: Line-field confocal optical coherence tomography (LC-OCT) is a new in vivo emerging technique that provides cellular resolution, allows deep imaging (400 µm) and produces real-time images in both the horizontal and vertical plane and in three dimensions. No previous description of different subtypes of melanocytic lesions and their correlation with histopathology and reflectance confocal microscopy has been reported. AIM: To describe the features of melanocytic lesions by LC-OCT and their correlation with histopathology and reflectance confocal microscopy (RCM) findings. METHODS: Selected melanocytic benign lesions and melanomas were imaged in vivo with RCM and LC-OCT at the Fundación Hospital Clinic (Barcelona, Spain). A minimum area of 4 × 4 mm (block image) at four depths (stratum granulosum, suprabasal, layer dermoepidermal junction and upper dermis) were acquired with RCM and a minimum of three cubes with LC-OCT. Horizontal, vertical sections and three-dimensional (3D) cubes of LC-OCT were matched with RCM (Vivablock two-dimensional composite mosaic) and histopathology, with ~5 µm lateral resolution accuracy (the same cell nuclei were measured in X, Y and Z) and evaluated by three observers experienced in using RCM and histopathology. RESULTS: In total, 12 melanocytic tumours (2 in situ melanomas, 2 invasive melanomas, 4 atypical naevi, 2 intradermal naevi, 1 compound naevus and 1 junctional naevus) were included. High correlation with 5 µm accuracy between RCM and LC-OCT was observed for each tumour. The 3D images of melanocytic lesions were obtained with cellular resolution and correlated with both RCM and histopathology, allowing an understanding of the architecture and precise correlation at the cellular level with RCM. Similarities between LC-OCT and RCM for the described diagnostic features and architecture (nests of melanocytic cells, ringed and meshwork pattern, and cellular details of tumour cells as dendritic and pagetoid cells) were confirmed. The main advantage of diagnosis by RCM fixed probe was the ability to produce larger scans of the lesion using mosaicing compared with an LC-OCT handheld probe. CONCLUSION: LC-OCT allows the architectural and cellular description of different types of melanocytic lesions. LC-OCT showed high correlation with histopathology (vertical sections) and RCM (horizontal sections) in melanocytic lesions. Diagnostic criteria for RCM were similar to those for LC-OCT.

Line-field confocal optical coherence tomography as a tool for three-dimensional in vivo quantification of healthy epidermis: A pilot study.

Epidermal three-dimensional (3D) topography/quantification has not been completely characterized yet. The recently developed line-field confocal optical coherence tomography (LC-OCT) provides real-time, high-resolution, in-vivo 3D imaging of the skin. This pilot study aimed at quantifying epidermal metrics (epidermal thicknesses, dermal-epidermal junction [DEJ] undulation and keratinocyte number/shape/size) using 3D LC-OCT. For each study participant (8 female, skin-type-II, younger/older volunteers), seven body sites were imaged with LC-OCT. Epidermal metrics were calculated by segmentations and measurements assisted by artificial intelligence (AI) when appropriate. Thicknesses of epidermis/SC, DEJ undulation and keratinocyte nuclei volume varied across body sites. Evidence of keratinocyte maturation was observed in vivo: keratinocyte nuclei being small/spherical near the DEJ and flatter/elliptical near the skin surface. Skin microanatomy can be quantified by combining LC-OCT and AI. This technology could be highly relevant to understand aging processes and conditions linked to epidermal disorders. Future clinical/research applications are to be expected in this scenario.