This is a partial hydatidiform mole. Note that there are only scattered grape-like villi. Such a partial mole occurs when an ovum is fertilized by two haploid sets of paternal chromosomes. This may occur with dispermy when two sperms fertilize a single ovum, or when a diploid sperm fertilizes an ovum, or if a haploid sperm fertilizes a diploid ovum. The result is triploidy with 69 chromosomes. Since a maternal set of chromosomes is present, a fetus develops, but it is malformed, and the pregnancy rarely goes to term. Only some of the villi are grape-like. Choriocarcinoma is a rare outcome of a partial mole.