## Distinguishing Complete from Partial Molar Pregnancy ### Key Histopathological Differences **Key Point:** Complete molar pregnancy (CMP) and partial molar pregnancy (PMP) differ fundamentally in fetal tissue presence and villous pathology, which is the most reliable discriminator. | Feature | Complete Molar Pregnancy | Partial Molar Pregnancy | |---------|--------------------------|------------------------| | **Fetal tissue** | Absent or minimal | Present (usually) | | **Villous edema** | Diffuse, marked | Focal, mild to moderate | | **Trophoblastic hyperplasia** | Diffuse, circumferential | Focal, patchy | | **Karyotype** | 46,XX (90%) or 46,XY (10%) — diploid androgenetic | 69,XXY or 69,XXX — triploid (2 paternal, 1 maternal) | | **hCG levels** | Markedly elevated (>100,000 mIU/mL) | Mildly to moderately elevated | | **Malignant potential** | 15–20% (gestational trophoblastic neoplasia) | 1–5% | ### Why This Matters Clinically **High-Yield:** The **absence of fetal parts combined with diffuse villous edema and circumferential trophoblastic hyperplasia** is pathognomonic for complete molar pregnancy. This finding alone mandates aggressive follow-up for persistent gestational trophoblastic disease (GTD). **Clinical Pearl:** Partial molar pregnancies often present later (16–20 weeks) because fetal tissue is present and may be viable initially, whereas complete molar pregnancies present earlier (8–12 weeks) with excessive bleeding and severe hyperemesis due to the absence of normal fetal development. **Mnemonic:** **CMP = Complete = No fetus + Diffuse edema + Diploid**; **PMP = Partial = Fetus present + Focal edema + Triploid** ### Ultrasound Correlation - **CMP:** "Bunch of grapes" appearance, no gestational sac, no fetal pole - **PMP:** Small fetus with abnormal placenta, cystic spaces in placental tissue [cite:Robbins 10e Ch 22] [cite:Park 26e Ch 11] 
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