As a rule, a complete mole is not accompanied by a fetus
As the name suggests, a partial mole is typically composed of two populations of villi, with only some villi being “molar,” i.e., hydropic.
Complete moles are characterized by diffuse, concentric, trophoblastic proliferation with central cisterns, while partial moles have polar trophoblastic proliferation that results in characteristic scalloped villous outlines and trophoblast (pseudo) inclusions.
The presence of a fetus or evidence of fetal development (e.g., nucleated red blood cells) indicates a partial mole.
Most partial hydatidiform moles are characterized by a triploid karyotype with two sets of chromosomes from the father and one set from the mother (e.g., 69, XXY). Most complete moles are diploid, with both sets of chromosomes of paternal origin.
