Gestational Trophoblastic Disease
Gestational trophoblastc diesase covers tumors and tumor-like diseases including; hydatidiform mole (complete and partial), invasive mole, choriocarcinoma and placental site trophoblastic tumor (PSTT).
It is important to recognise hydatidiform moles as it is associated with an increased risk of invasive mole (trophoblastic mole) or choriocarcinoma. Moles are presented histologically as cystic swelling of chorionic villi with trophobalst proliferation. Hydatidiform moles are diagnosed usually in early pregnancy (9 week) by pelvic sonogram. They are mostly seen in teenagers and between ages of 40-50 years.
Complete mole results from fertilization of an egg that has lost its female chromosomes, and so the genetic material is completely derived paternally.
A. One sperm fertilizes an empty ovum, and only paternal chromosomes exist. Karyotype is 46XX . 90% percent of complete moles occur as homozygous complete mole.
B. Two sperm fertilize one egg and the fertilized egg has 46XX or 46XY karyotype. 10 percent of the complete moles occur as heterozygous complete mole.
C. Two sperms fertilize an ovum and the fertilized egg has 69XXX, 69XXY, 69XYY karyotype. The case is called as triploid partial mole.
Classic hidatidiform mole appears with delicate, friable mass of thin walled, translucent, cystic, grapelike structures consisting of swollen edematous (hyrophic) villi.
In complete mole microscopic abnormalities involve all or most of the villous tissue.
In partial moles, only a fraction of villi are enlarged and edematous. The trophoblastic hyperplasia is less marked than in complete moles.
Partial and complete moles result in miscarriage or curretage. Abnormal villous enlargement is seen with ultrasound. In complete moles human chorionic gonadotropin (HCG) level exceeds the normal range. Mostly moles are removed successfully by curretage. For 6 months after removing the moles the HCG levels are monitored. If HCG levels keep encreasing, persistent or invaisve mole may be present which is seen in 15% of the cases and develops more common in complete moles. 2.5% of the complete moles give rise to gestational choriocarcinoma.
Robbins & Cotran Pathologic Basis of Disease; 1039