Markers of the pre-metastatic niche “knock on the door” of metastasis-free cervical lymph nodes in patients with oral cancer

Aim: To assess expression of some markers of the pre-metastatic niche (PMN) in lymph nodes (LNs) of oral cancer patients. Materials: LNs from metastatic-free neck dissections (LN0/N0, N = 43) and metastatic-free LNs in the vicinity of metastasis-containing LNs (LN0/N+, N = 30) were immuno-histochemically stained for lysyl oxidase (LOX), fibronectin (FN), vascular-endothelial growth factor receptor (VEGFR)-1 and matrix metalloproteinase (MMP)-9. Staining was assessed as 0 (no or weak staining), 1 (strong stain in 25% cells or extracellular area), 2 (same as 1 but in up to 50%) and 3 (same as 1 but in > than 50% of cells/area). Assessment was performed in the lymph node capsule (CAP), sub-capsular sinus (SCS) and medullary sinus (MS). In addition, sections were stained with picrosirius red and examined with polarized microscopy for assessing the distribution of polarization colors of the collagen fibers in the LN capsular area. Results: All examined LNs were positive for markers of the PMN. In general, the distribution and intensity of the immunoreactivity was similar between the LN0/N0 and LN0/N+, with only a few differences regarding expression of LOX in the capsule (p = 0.002) and VEGFR1 and MMP9 in the SCS (p = 0.023 and p < 0.001, respectively). Picrosirius red stain and polarized microscopy revealed a disrupted arrangement and distribution of the collagen fibers in both LN0/N0 and LN0/N + . Conclusion: Markers for PMN were shown for the first time to be expressed in cervical LN0/N0 from patients with oral cancer, suggesting the increased permissive pathway remotely paved by the primary oral tumor for the incoming metastatic cells.