FIGURE 20-1 Complete hydatidiform mole. A. Gross specimen with characteristic vesicles of variable size. (Used with permission from Dr. Brian Levenson.) B. Low-magnification photomicrograph shows generalized edema and cistern formation (black asterisks) within avascular villi. Haphazard trophoblastic hyperplasia is marked by a yellow asterisk on the right. (Used with permission from Dr. Erika Fong.)
The degree of histological changes, karyotypic diferences, and the absence or presence of embryonic elements are used to clas siy them as either complete orpartial moles. hese two also vary and postevacuation GTN. Of the two, GTN more frequently follows complete hydatidiform mole.
A complete mole has abnormal chorionic villi that grossly appear as a mass of clear vesicles. These vary in size and often hang in clusters from thin pedicles. In contrast, a partial molar pregnancy has focal and less advanced hydatidiform changes and contains some fetal tissue. Both forms of moles usually fill the uterine cavity, but they rarely may be tubal or other forms of ectopic pregnancy (Hassadia, 2012; Sebire, 2005).
An ethnic predisposition is seen with hydatidiform mole, which has increased prevalence in Asians, Hispanics, and American Indians (Drake, 2006; Lee, 2011; Smith, 2006). he incidence in the United States and Europe has been relatively constant at 1 to 2 per 1000 deliveries (Eysbollts, 2016; Lee, 2011).
The strongest risk factors are age and a prior hydatidiform mole. Women at both extremes of reproductive age are most vulnerable. Speciically, adolescents and women aged 36 to 40 years have a twofold risk, but those older than 40 have an almost tenfold risk (ltman, 2008; Sebire, 2002a). With a prior complete mole, the risk of another mole is 0.9 percent, and with a previous partial mole, the rate is 0.3 percent. Mter two prior complete moles, approximately 20 percent of women have a third mole (Eagles, 2015).
Molar pregnancies typically arise from chromosomally abnormal fertilizations Figure 20-2. Complete moles most often have a diploid chromosomal composition (Table
These usually are 46,X and result from androgenesis, meaning both sets of chromosomes are paternal in origin. The chromosomes of the ovum are either absent or inactivated. The ovum is fertilized by a haploid sperm, which then duplicates its own chromosomes after meiosis. Less commonly, the chromosomal pattern may be 46,Y or 46,X and due to fertilization by two sperm, that is, dispermic ertilization or dispermy (Lawler, 1991; Lipata, 2010).
23,Y
FIGURE 20-2 Typical pathogenesis of complete and partial moles.
A. A 46,XX complete mole may be formed if a 23,x-bearing haploid sperm penetrates a 23,X-containing haploid egg whose genes have been "inactivated." Paternal chromosomes then duplicate to create a 46,XX diploid complement solely of paternal origin.
B. A partial mole may be formed if two sperm-either 23,X-or 23,Y-bearing-both fertilize (dispermy) a 23,X-containing haploid egg whose genes have not been inactivated. The resulting fertilized egg is triploid with two chromosome sets being donated by the father. This paternal contribution is termed diandry ..
aTypical karyotypes.