The nasopalatine duct, the most dominant developmental tubule formed by the emergence of premaxilla and both sides of anterior palatal processes. This duct normally disappears in humans but remains latent and provides communication between the oral and nasal cavities in some mammals. However, the duct is obliterated and degenerated before birth in human, thus the persisting or patent nasopalatine duct in postnatal life is considered a developmental anomaly. Two cases of patent nasopalatine duct were presented in this study. Although the ducts were not sectioned longitudinally, they were probably connected each other and contained mucous materials secreted from the associated mucous glands. In the immunohistochemical study the ductal epithelium was consistently positive for the growth-related biomarkers including TGFβ1, c-erbB2, EGFR, CTGF, FGFb, HGF, eiF5A, FAK, and pAKT. And many columnar epithelial cells of the duct were positive for PCNA. Particularly, TNFα was clearly positive in the ductal epithelium together with β-defensin-2, -3 and MMP-3, -9. These findings may imply that the ducts have a growth potential postnatally and also can induce inflammatory reaction. Therefore, it was presumed that the present cases of patent nasopalatine ducts were caused by the latent proliferation of ductal epithelia in the vascular environment of nasopalatine canal without cyst formation, and also suggested that the patent nasopalatine ducts connected with functioning mucous glands were partly open to oral/nasal cavity and should be differentially diagnosed from the nasopalatine duct cyst.