PKD1 and neoplasm: In this work, the expression of PKD1, PKD2, and PKD3 isoforms at the protein level was tested in situ in a series of HNSCCs from different anatomical regions using a sensitive immunohistochemistry protocol and the results were correlated with the clinicopathological parameters of the tumors, including localization, tumor grade, TNM (tumor, node, metastasis) stage and survival.