Background and objectives: TNM classification and grading describe tumourbiological parameters of the oral squamous cell carcinoma (OSCC) only incompletely. In solid malignancies the influence of immunological parameters on invasiveness, metastatic potential and prognosis could be shown. Yet there are no studies quantitatively analyzing the macrophage polarization in OSCC specimens. The aim of this study was to correlate the macrophage polarization in tumour and regional lymph node specimens with histopathological parameters (N-, L-, V-, Pn-status, grading).

Methods: Oral squamous cell carcinoma samples ( n = 30), metastatic- and non-metastatic lymph node samples were investigated by immunohistochemistry. Automated staining with an LSAB-kit was used to detect CD68, CD11c, CD163 and MRC1 positive cells. Complete digitalization of all samples using whole slide imaging and semiquantitatively assessment of the number of stained cells per area was performed.

Results: In tumours with primary lymph node metastasis (N+) compared to N0 tumours, a significantly ( p < 0.05) increased cell count of CD68, CD11c, CD163 and MRC1 positive cells in the epithelial fraction of the cancer tissue could be shown. The ratio between CD163 positive cells (indicating predominantly M2-macrophages) and CD68 positive cells (staining all macrophages) was significantly ( p < 0.05) increased in N+ tumours compared to N0 neoplasms. The metastatic lymph nodes showed in contrast to the non-metastatic lymph nodes a significantly (p < 0.05) increased CD163 cell count (M2-macrophages) in the interfollicular zone. Additionally, the CD163 to CD68 ratio in the interfollicular zone was significantly ( p < 0.05) higher in the metastatic lymph nodes compared to the non-metastatic nodes.

Conclusion: These results show an increased macrophage infiltration as well as an increased M2-polarization in primary lymphogenic metastatic OSCC. In particular, the macrophages that migrated into the epithelial tumour fraction seem to be of special biological importance. The increased M2-polarization in the metastatic lymph nodes might be a consequence of the cancer-induced peripheral immune tolerance.