Gestational trophoblastic disease (GTD) includes hydatidiform moles and malignant tumors. Which chromosomal composition characterizes a complete hydatidiform mole?
- A 69, XXX or 69, XXY (triploid) — one set of maternal plus two sets of paternal chromosomes
- B 45, X (monosomy) — resulting from meiotic nondisjunction
- C 46, XX (diploid) — entirely androgenetic (derived from paternal haploid set that duplicates) ✓
- D 46, XY (diploid) — one maternal and one paternal contribution with normal fertilization
Explanation
A complete hydatidiform mole has a diploid karyotype (46,XX most commonly, or 46,XY) that is entirely androgenetic — arising from fertilization of an enucleate egg by one sperm that duplicates (or two sperm). All chromosomes are of paternal origin; maternal chromosomes are absent. Complete moles show diffuse trophoblastic hyperplasia, no fetal/embryonic tissue, and higher malignant potential (~2–3% develop choriocarcinoma). Partial moles are triploid (69,XXX or 69,XXY or 69,XYY) from fertilization of a normal egg by two sperm, contain some fetal tissue, and have very low malignant potential.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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