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.