Correct Answer: D. Partial mole
Partial mole (partial hydatidiform mole) is NOT classified as a gestational trophoblastic neoplasm (GTN). This is the critical discriminator. GTN refers specifically to malignant or potentially malignant trophoblastic tumors that arise from gestational tissue. Partial mole is a benign hydatidiform mole — a non-neoplastic abnormality of pregnancy characterized by abnormal placental development with some fetal tissue present (triploid karyotype, usually 69,XXY or 69,XXX). While partial moles can rarely progress to persistent GTD or GTN in ~1–5% of cases, the partial mole itself is classified as a molar pregnancy (benign), not a neoplasm. In contrast, invasive mole, choriocarcinoma, and placental site trophoblastic tumor are all true GTNs — they are malignant tumors arising from trophoblastic tissue. Per WHO and Indian gynecology textbooks (DC Dutta, Jeffcoate's), GTN classification includes only invasive mole, choriocarcinoma, and placental site trophoblastic tumor (PSTT). Partial mole belongs to the category of hydatidiform moles (benign), not GTN.
Why the other options are wrong
A. Invasive mole — Invasive mole (chorioadenoma destruens) IS a true GTN. It is a malignant tumor where trophoblastic tissue invades the myometrium and beyond, arising from a complete mole. It can metastasize and is included in the WHO classification of GTN. This is a neoplasm by definition. B. Placental site trophoblastic tumor — PSTT IS a GTN — a rare malignant tumor arising from intermediate trophoblastic cells at the placental implantation site. It occurs after any pregnancy (molar or non-molar) and is characterized by high hCG levels and potential for metastasis. It is explicitly listed in WHO GTN classification. C. Choriocarcinoma — Choriocarcinoma IS a GTN — the most aggressive trophoblastic malignancy. It arises from syncytiotrophoblast and cytotrophoblast, produces very high hCG, and metastasizes early (especially to lungs, brain, liver). It is the prototypical GTN and is always included in GTN classification.
High-Yield Facts
- Partial mole is a benign hydatidiform mole (triploid, 69,XXY/XXX), NOT a GTN — it has some fetal tissue and lower malignant potential (~1–5%).
- GTN classification includes only three entities: invasive mole, choriocarcinoma, and placental site trophoblastic tumor — all are malignant.
- Complete mole (diploid, 46,XX or 46,XY) has 15–20% risk of GTN; **partial mole** has 1–5% risk, making it lower-risk.
- Invasive mole invades myometrium and beyond; choriocarcinoma is the most aggressive with early metastasis; PSTT arises from intermediate trophoblast.
- hCG levels are markedly elevated in choriocarcinoma and invasive mole; PSTT may have lower hCG; partial mole has lower hCG than complete mole.
Mnemonics
GTN = Malignant Only (3 types) Invasive mole, Choriocarcinoma, Placental site trophoblastic tumor — remember ICP as the three true GTNs. Partial mole is NOT in this list. Molar Pregnancy vs GTN Molar = Benign (complete or partial hydatidiform mole). GTN = Malignant (invasive mole, choriocarcinoma, PSTT). Partial mole stays benign unless it progresses.
NBE Trap
NBE exploits the confusion between hydatidiform moles (benign pregnancy abnormalities) and gestational trophoblastic neoplasms (malignant tumors). Students often group all molar-related conditions together and mistakenly include partial mole in GTN, forgetting that GTN is defined by malignancy.
Clinical Pearl
In Indian clinical practice, all patients with molar pregnancy (complete or partial) require hCG monitoring and ultrasound follow-up for 6–12 months post-evacuation. However, only those who develop persistent GTD/GTN (rising hCG, imaging evidence) are classified as having GTN and require chemotherapy — partial mole patients have lower progression risk and often need only surveillance, not chemotherapy upfront.
_Reference: DC Dutta's Textbook of Obstetrics (8th ed.), Ch. 22; Jeffcoate's Principles of Gynaecology (8th ed.), Ch. 24; WHO Classification of Gestational Trophoblastic Neoplasia (2015)_