Digital Dermatopathology of Scabies: HE-Compatible VIS-NIR Hyperspectral Imaging as a Label-Free Proof-of-Concept Approach.

Background: Scabies, caused by Sarcoptes scabiei var. hominis, remains difficult to confirm histologically when parasites are sparse or fragmented. Conventional microscopy is particular but limited by small sample size, tissue destruction, and observer dependence. Objective: To evaluate visible-near-infrared hyperspectral imaging (VIS-NIR HSI) as a label-free optical method for detecting S. scabiei in human skin sections and to assess its compatibility with routine HE staining. Methods: Formalin-fixed, paraffin-embedded (FFPE) skin tissue from six patients with histologically verified scabies was analysed using VIS-NIR HSI (500-1000 nm). Unstained sections mounted on CaF2 substrates and parallel HE-stained slides were imaged. Spectral datasets were processed by principal component analysis and segmentation to distinguish mite structures from epidermal and dermal compartments. Results: The chitin-rich mite exoskeleton exhibited a reproducible reflectance slope in the near-infrared range (R850/R550 > 1.5), clearly separating parasite from host tissue (R850/R550 < 1.0). PCA confirmed consistent cluster separation across all cases (ΔPC ≈ 3.7 ± 0.2). These contrasts remained detectable in HE-stained sections, validating applicability to conventional slides. Conclusions: VIS-NIR HSI enables reliable, label-free detection of S. scabiei mites in both unstained and HE-stained human skin tissue. By combining morphological and biochemical information in a single modality, HSI represents a promising adjunct to digital dermatopathology and may improve diagnostic sensitivity in challenging or atypical cases.