Abstract
Morphology and distribution of melanocytes are critical imaging information for the diagnosis of melanocytic lesions. However, how to image intratumoral melanocytes noninvasively in pigmented skin tumors is seldom investigated. Third-harmonic generation (THG) is shown to be enhanced by melanin, whereas high accuracy has been demonstrated using THG microscopy for in vivo differential diagnosis of nonmelanocytic pigmented skin tumors. It is thus desirable to investigate if label-free THG microscopy was capable to in vivo identify intratumoral melanocytes. In this study, histopathological correlations of label-free THG images with the immunohistochemical images stained with human melanoma black (HMB)-45 and cluster of differentiation 1a (CD1a) were made. The correlation results indicated that the intratumoral THG-bright dendritic-cell-like signals were endogenously derived from melanocytes rather than Langerhans cells (LCs). The consistency between THG-bright dendritic-cell-like signals and HMB-45 melanocyte staining showed a kappa coefficient of 0.807, 84.6% sensitivity, and 95% specificity. In contrast, a kappa coefficient of −0.37, 21.7% sensitivity, and 30% specificity were noted between the THG-bright dendritic-cell-like signals and CD1a staining for LCs. Our study indicates the capability of noninvasive label-free THG microscopy to differentiate intratumoral melanocytes from LCs, which is not feasible in previous in vivo label-free clinical-imaging modalities.
Highlights
Melanocytes present in the skin and hair follicles play a crucial role in the cutaneous pathophysiology
When normal skin tissue was observed from a vertical section by Harmonic generation microscopy (HGM) ex vivo, we found the Third-harmonic generation (THG)-bright dendritic cells were located in the stratum basale but not in the suprabasal layers [Fig. 2(a)]
To investigate if Langerhans cells (LCs) can be enhanced in THG microscopic images, the blinded evaluation of THG images was compared to the record of THG images acquisition for lesions or normal counterparts and, compared to the final pathological judgment for diagnosis
Summary
Melanocytes present in the skin and hair follicles play a crucial role in the cutaneous pathophysiology. Keratinocyte-derived factors, including endothelin 1 (ET1), nerve growth factor (NGF), α-melanocyte-stimulating hormone (α-MSH), adrenocorticotrophic hormone, prostaglandin E2 (PGE2), prostaglandin F2α (PGF2α), and β-endophin, have been demonstrated to play a role in melanocyte. Atypical melanocytes with pagetoid spread, horizontal, or vertical growth are important diagnostic histopathological criteria for malignant melanoma.[8] The majority of melanocytes reside in the basal epidermis, where melanocytes are surrounded by keratinocytes with an approximate ratio of one melanocyte per five to six keratinocytes, and form epidermal melanin units.[3] It has been demonstrated that melanocytic
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