Early diagnosis of melanoma is an ongoing challenge in dermatology and oncology. There is a special subgroup of melanocytic lesions that can be clinically and dermoscopically indistinguishable from early melanoma. The aim of the study was to improve the in vivo diagnostic possibilities for the differentiation of dermoscopic equivocal melanocytic lesions based on combination of multiphoton tomography (MPT) and optical coherence angiography (OCA). A multiphoton optical score (MPOS) for quantitative assessment of the melanoma features revealed by MPM was developed. OCA images were processed to calculate the vessel densities and the total lengths thin and thick vessels. Histopathological analysis separated the equivocal lesions into benign, melanoma in situ, and invasive melanoma. The MPOS value of benign lesions was significant lower than for the malignant ones. Quantitative analysis of OCA images revealed that the invasive melanoma type has the highest vessel density. The combined use of multiphoton tomography with MPOS calculation and quantification of optical coherence angiography data demonstrated a potential to discriminate all dermoscopic equivocal melanocytic lesions in vivo.
The clinical diagnosis of melanocytic lesions is an ongoing medical challenge. Non-invasive tools and technologies can help to distinguish equivocal lesions. The aim of the study was to improve the in vivo diagnostic possibilities for the differentiation of benign and malignant melanocytic lesions based on combination of three imaging label-free modalities (multiphoton tomography, fluorescence lifetime imaging and optical coherence angiography). Thirty-two melanocytic lesions were studied, using multiphoton tomography, fluorescence lifetime imaging and optical coherence angiography. Multiphoton tomography features of benign melanocytic nevi were characterized by the normal morphology of both the keratinocytes and the nevus cell nests surrounded by collagen. Dysplastic nevi were characterized by their increased intercellular distances and enlarged cell nuclei. Melanomas showed the presence of melanocytes and dendritic structures in all layers of the epidermis. Analysis of the metabolic state revealed that melanomas and dysplastic nevi were characterized by enhanced glycolysis. Optical coherence angiography shows that benign nevi had regular vascular networks and equal numbers of thin and thick vessels. Vascular networks of dysplastic nevi were characterized thin curved vessels. Thick irregular spiral vessels formed a dense microvascular network of melanomas.