Abstract
Lymphangiogenesis makes an important contribution to the tumour microenvironment (TME), but little is known about this in oral squamous cell carcinoma (OSCC). Archival formalin-fixed paraffin-embedded specimens (28 OSCC, 10 inflamed and 6 normal oral mucosa controls) were processed using immunohistochemistry (IHC) with antibodies against lymphatic markers D2-40 (podoplanin), LYVE-1, VEGFR3 and Prox1. After the endothelial cells had been highlighted by the various markers for lymphatic endothelium, the positive stained cells and vessels were identified and counted in a systematic manner to determine microvessel density. Double-labelling immunofluorescence (DLIF) was used to investigate the specificity of D2-40 and LYVE-1 to lymphatic endothelial cells (LECs) as opposed to blood ECs. There was higher D2-40 and Prox1 lymphatic vessel density (P = .001) in the OSCC group when compared with both control groups. Some malignant keratinocytes expressed lymphatic markers, as did a much smaller number of epithelial cells in the control groups. DLIF showed that no vessels co-expressed D2-40/CD34 or LYVE/CD34. Some D2/40(+) LVs were LYVE-. D2-40 was the most specific LEC marker in OSCC tissues. These results establish that the OSCC TME contains significantly more lymphatic vessels expressing D2-40 and Prox1 than the control groups, which may play a role in facilitating lymphatic invasion and metastases.