Which statement best differentiates hydatidiform mole from gestational trophoblastic neoplasia (GTN)?

• A. Hydatidiform mole presents with uterine size greater than dates and may have fetal parts or none; GTN can develop after a normal pregnancy, molar pregnancy, or miscarriage and is often invasive with elevated hCG.
• B. GTN can develop only after molar pregnancy.
• C. Hydatidiform mole always contains a live fetus.
• D. GTN is never associated with vaginal bleeding.

Answer: (A)

The key idea is that hydatidiform mole is a specific type of gestational trophoblastic disease marked by abnormal fertilization, whereas gestational trophoblastic neoplasia (GTN) is a spectrum of persistent trophoblastic disease that can follow any pregnancy event and tends to behave more invasively with rising or persistent hCG.

Hydatidiform mole often presents with a uterus that is enlarged for dates and, depending on the type, may contain fetal tissue or none at all (complete mole typically has no fetus; partial mole may have fetal parts). GTN, on the other hand, can develop after a normal pregnancy, a molar pregnancy, or a miscarriage, and it is characterized by persistent or invasive disease with elevated or plateauing hCG levels.

The other statements are less accurate: GTN is not limited to following a molar pregnancy; hydatidiform mole does not always contain a live fetus; and GTN can be associated with vaginal bleeding.