The mucin-type transmembrane glycoprotein podoplanin (also known as T1alpha, gp38 or Aggrus) is well established as one of the lymphatic-specific markers. Podoplanin was also reported to be associated with tumor-induced platelet aggregation and tumor metastasis. Here, we generated a novel monoclonal antibody (clone; 7B10) that specifically recognized human podoplanin, as assessed by enzyme-linked immunosorbent assay, Western blot analyses, immunohistochemistry and flow cytometry. 7B10 stained not only lymphatic vessels but also type I alveolar cells in the lung, podocytes in the kidney and myoepithelial cells in the breast. In addition, podoplanin expression was analyzed by immunostaining on tissue microarrays that included 12 different cancer types using 7B10. Consequently, we found that podoplanin was expressed by cancer cells derived from esophagus, lung, liver, colon and breast, as well as lymphatic endothelial cells. These findings suggest a potential role of podoplanin in tumor progression in diverse types of human cancers.