Characterization of microvascular remodeling in metastatic sentinel lymph nodes via skeletonization framework generated by ultrasound localization microscopy.

Lymphatic spread to the sentinel lymph node (SLN) represents the primary pathway for early-stage breast cancer metastasis. Given that metastatic progression is fundamentally driven by pathological angiogenesis, high-resolution imaging and quantification of SLN microvasculature are critical for assessing tumor spread. In this study, we applied ultrasound localization microscopy (ULM) to a rabbit VX2 breast tumor model and developed a skeletonization-based analytical framework to quantify lymphatic microvascular morphology. This approach extracts vascular centerlines from grayscale ULM images to derive five morphological parameters that characterize the microvascular architecture. Our results demonstrate that ULM achieves sub-wavelength visualization of the targeted regions, revealing the tortuous and dense neovascular networks characteristic of metastatic SLNs. Qualitative observations and quantitative metrics consistently identified marked architectural divergences between metastatic and normal SLNs. Specifically, metastatic nodes exhibited a denser, more disordered vascular organization that recapitulated the microvascular patterns of primary tumors, distinct from the organized hierarchy of normal nodes. These findings provide an experimental foundation for clinical translation, suggesting that ULM-based microvascular characterization holds significant promise as a non-invasive modality for diagnosing breast cancer lymphatic metastasis.