Hydatidiform Mole

Pathophysiology

1) structure is an abnormal placenta 2) two forms are described – complete mole and partial mole 3) complete mole – when an ovum that lacks DNA is fertilized 4) partial moles – from fertilization of a normal ovum with two sperm or from fertilization of a normal ovum with one abnormal sperm (46 or 69 chromosomes) 5) partial moles have a fetus that dies before 10 weeks, with fetal tissue usually present

Signs and Symptoms

1) usually presents at 11-25 weeks 2) striking uterine enlargement 3) heavy bleeding 4) passage of grape-like tissue fragments

Characteristic Test Findings

Laboratory – 1) strikingly elevated HCG with a rapid rate of increase Radiology – 2) “snow storm” appearance on ultrasound

Histology/Gross Pathology

Complete mole – 1) placenta has markedly swollen chorionic villi that look like grapes 2) no embryo is present 3) very few if any vessels in villi 4) varying stages of trophoblastic proliferation; atypia with syncytiotrophoblast, cytotrophoblast, and intermediate trophoblast all occurring Partial mole – 5) some normal and some swollen and abnormal villi (but much less in number than in complete mole) 6) some blood vessels 7) trophoblastic proliferation is focal only

Associated Conditions

1) hemorrhage 2) infection 3) perforation of uterus 4) embolism 5) choriocarcinoma in 2% of complete moles (does not occur in partial moles) 6) if the mole has invaded the underlying myometrium or has penetrated through it to the broad ligament, there is a 25-40% chance of spread to distant sites, especially the lungs

Inheritance/Epidemiology

1) complete mole – all genes are of paternal origin (46XX) 2) risk is related to maternal age with a bimodal distribution (< 15 years and > 40 years) 3) risk for occurrence in Asian women is 25 times greater than in white women 4) risk for recurrence is increased 20 times after first mole

Treatment

1) suction curettage of uterus with close follow-up of HCG levels 2) chemotherapy is required if HCG remains elevated 3) hysterectomy if no further pregnancies are planned

Tips for USMLE

1) complete moles have no fetal parts; partial moles usually have fetal parts 2) choriocarcinoma is a risk following complete moles only