A total of 297 samples of hydropic villi were classified according to DNA polymorphisms as androgenetic moles, dispermic triploids, or biparental diploids. A subset of 267 appropriate samples was included in the study. Most of the macroscopically diagnosed complete mole cases were genetically androgenetic in origin. The partial mole cases consisted of 30 androgenetic moles and 12 dispermic triploids. For the 59 cases macroscopically categorized as hydropic abortion, the genetic analysis revealed 38 androgenetic moles, seven dispermic triploids and 14 biparental diploids. These results showed that a new diagnostic method was required for the management of patients with hydropic villi. We identified the TSSC imprint gene of which expression was shown in normal and partial mole villi but was silenced in complete mole villi. Immunohistochemistry using the TSSC3 antibody demonstrated its efficacy as the differential diagnostic method. TSSC3 play an important role in the differentiation from trophoblast stem cells to progenitors and/or labyrinth trophoblast through the TSSC3/PI3K/Akt/Mash2 signaling pathway.