Second-harmonic generation imaging analysis can help distinguish sarcoidosis from tuberculoid leprosy

Agradecimentos: This study was supported by the São Paulo Research Foundation—FAPESP (Grant Nos. 2016/22927-7, 2017/17149-8, and 11/51959-0) and by Coordination of Superior Level Staff Improvement (CAPES) (Grant No. 01-P-3368/2017). We would like to express our thanks for the access to equipment and assistance provided by the National Institute of Science and Technology on Photonics Applied to Cell Biology (INFABIC), which is cofounded by FAPESP (Grant No. 2014/50938-8) and by National Council for Scientific and Technological Development (CNPq) (Grant Nos. 465699/2014-6 and 312049/2014-5). We are also grateful to Adilson A. Piaza and Mercedes F. Santos for assistance in photographic documentation, Ana C. Piaza and Luzia A. Magalhães for technical assistance, and Cleide A.M. Silva and Juliana L.P. Argenton for statistical assistance Abstract: Sarcoidosis and tuberculoid leprosy (TL) are prototypes of granulomatous inflammation in dermatology, which embody one of the histopathology limitations in distinguishing some diseases. Recent advances in the use of nonlinear optical microscopy in skin have enabled techniques, such as second-harmonic generation (SHG), to become powerful tools to study the physical and biochemical properties of skin. We use SHG images to analyze the collagen network, to distinguish differences between sarcoidosis and TL granulomas. SHG images obtained from skin biopsies of 33 patients with TL and 24 with sarcoidosis retrospectively were analyzed using first-order statistics (FOS) and second-order statistics, such as gray-level co-occurrence matrix (GLCM). Among the four parameters evaluated (optical density, entropy, contrast, and second angular moment), only contrast demonstrated statistical significance, being higher in sarcoidosis (p = 0.02||4908.31 versus 2822.17). The results may indicate insufficient differentiating power for most tested FOS and GLCM parameters in classifying sarcoidosis and TL granulomas, when used individually. But in combination with histopathology (H&E and complementary stains, such as silver and fast acid stains), SHG analysis, like contrast, can contribute to distinguishing between these diseases. This study can provide a way to evaluate collagen distribution in granulomatous diseases FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Aberto