PhD Scientific Days 2026

Poster Session 2.E - Pathological and Oncological Sciences

Polarization-Dependent SHG Analysis of Collagen Structure for Tumor Border Assessment in Basal Cell Carcinoma

Name of the presenter

Kubacska, Renáta

Institute/workplace of the presenter

Department of Dermatology, Venereology and Dermatooncology, Semmelweis University Doctoral School

Authors

Renáta Kubacska^1,2, Dániel Rózsa², Dr. Róbert Szipőcs²
1: Department of Dermatology, Venereology and Dermatooncology, Semmelweis University Doctoral School
2: HUN-REN Wigner Research Centre for Physics

Text of the abstract

Introduction
Basal Cell Carcinoma (BCC) is the most common malignant skin neoplasm in Caucasians. Its poorly defined tumor margins reduce the reliability of conventional imaging, making margin assessment a persistent clinical challenge. Second harmonic generation (SHG) microscopy is a label-free nonlinear optical technique sensitive to fibrillar collagen orientation, and therefore it could be well-suited for quantitative tumor border assessment.

Aims
To investigate the polarization-dependent SHG response of BCC collagen in the tumor environment and at the tumor border, and to assess whether pixel-resolved orientation heatmaps can improve tumor margin delineation compared to FFT (Fast Fourier Transformation) based methods.

Method
SHG measurements were performed on BCC tissue sections with excitation polarization rotated in a 180 degree range by rotating a /2 waveplate from 255 to 345 degrees in 5-degree increments (19 images per mosaic). Two regions were examined: a homogeneous central area (3×3 mosaic) and an inhomogeneous tumor border region (8×5 mosaic). Five ROIs per mosaic were evaluated and the dominant SHG intensity maximum per ROI was identified. Then pixel-by-pixel analysis can be applied: a dominant orientation value is assigned to each pixel from its SHG intensity curve and can be visualized as a color-coded orientation heatmap.

Result
In the external tumor area, all five ROIs showed well-defined single SHG maxima in the narrow 290–295 polarisation degree range, consistent with parallel, well-aligned collagen fibers. At the tumor border, ROIs showed shifted maxima (330–335 degrees) or dual maximums (e.g. 285 and 335 degrees), consistent with a multi-directional collagen arrangement. The dominant fiber orientations of the two regions differed by approximately 40 degrees.

Conclusion
Polarization-dependent SHG imaging revealed spatial heterogeneity in collagen fiber alignment in BCC, consistent with patterns previously identified by FFT-based methods. Unlike FFT-based methods, where unit-cell subdivision limits spatial detail, pixel-resolved orientation heatmaps can preserve full resolution and provide more detailed structural maps. These results support P-SHG microscopy as a quantitative tool for BCC border assessment.

Funding
Supported by the EKÖP-KDP fellowship programme.