Expression of podoplanin in the invasion front of oral squamous cell carcinoma is not prognostic for survival

Podoplanin is involved in actin remodeling of the cytoskeleton of tumor cells and may promote tumor cell invasion by increasing cell motility and formation of filopodia-like membrane protrusions. Podoplanin is expressed in a variety of tumors, but its role in head and neck cancer, particularly in oral squamous cell carcinoma, remains unclear. We studied podoplanin expression by immunohistochemistry in 92 oral squamous cell carcinomas (OSCC) using a monoclonal antibody against an epitope of podoplanin (D2-40). In terms of the number of stained cells, 34 OSCC (38 %) had low podoplanin expression (less than 33 % of cells), 33 (36 %) showed moderate expression (between 34 and 66 % of cells), and 21 (22 %) showed high expression. The intensity of immunostaining was strong in 26 (28 %) cases, moderate in 36 (40 %), and weak or negative in the remaining 30 tumors (32 %). Immunohistochemical expression of podoplanin was associated with a tumor histological grade. A diffuse pattern of podoplanin expression significantly decreased in moderately differentiated (37 %) and poorly differentiated (20 %) carcinomas compared to well-differentiated (43 %) carcinomas. In addition, the focal expression of podoplanin in the invasion front of the tumor, without expression in the tumor center, was observed in 72 % of well-differentiated tumors, 27 % of moderate tumors, and 0 % of poorly differentiated tumors. Moreover, a trend was found toward an association of diffuse podoplanin staining with the development of second primary carcinomas (13 %), in contrast to its expression in the invasion front (3 %). No association was observed between podoplanin expression and nodal metastasis.