PDPN (podoplanin) is mucin-type membrane glycoprotein with expression in a diverse range of tissues and cell types including lung alveolar cells, kidney podocytes, lymphatic endothelial cells, and neural tissues. PDPN is a required protein in the development of the lungs, lymphatic system and the heart, and it separately may play a role in immune response to fungal infections. In immunohistochemistry, PDPN has cytoplasmic and membranous staining in the lymphatic endothelium, breast myoepithelium, podocytes, dendritic cells and mesothelium. It is a sensitive and specific marker for the lymphatic endothelium, and it is used as an endothelial cell marker in determining lymphatic invasion in tumors. References: Clin Inv. 118 (11): 3725–37, PMID: 18924607; Frontiers in Immunology. 2012. 3: 283. doi:10.3389/fimmu.2012.00283, PMID: 22988448