Paper II
Question
Discuss the gross and microscopic appearance (with a diagram) of hydatidiform mole.
Answer
Hydatidiform mole is the most common form of gestational trophoblastic disease, characterized by abnormal chorionic villous development.
Gross appearance
- Complete mole: uterine cavity filled with a mass of thin-walled, translucent, grape-like grossly visible vesicles (dilated hydropic villi), with no identifiable embryo/fetal tissue
- Partial mole: a mixture of hydropic vesicular villi and normal-appearing villi, often with identifiable embryonic/fetal tissue (though usually non-viable)
(A labelled diagram cannot be rendered in this text-based answer; the description above covers the key features — grape-like vesicles, absence/presence of fetal parts — that would be annotated on a gross specimen diagram.)
Microscopic appearance
Complete mole
- Diffuse hydropic (oedematous) swelling of essentially all chorionic villi
- Marked circumferential trophoblastic hyperplasia (both cytotrophoblast and syncytiotrophoblast) surrounding the villi
- Absence of fetal blood vessels within villi, and absence of any embryonic/fetal tissue
- Karyotype: typically 46,XX (entirely paternal, from duplication of a single sperm’s genome after fertilizing an empty ovum)
Partial mole
- Two populations of villi — some hydropic, some of relatively normal size
- Focal, mild trophoblastic hyperplasia (less than complete mole)
- Scalloped (irregular) villous contours with prominent trophoblastic stromal inclusions
- Presence of fetal blood vessels (containing nucleated red cells) and often identifiable embryonic/fetal tissue
- Karyotype: typically triploid (69,XXY), from fertilization of a normal ovum by two sperm
Clinical significance
- Both types carry a risk of progression to persistent/invasive gestational trophoblastic neoplasia, requiring monitoring with serial serum beta-hCG levels after evacuation; complete moles carry a higher risk of subsequent choriocarcinoma than partial moles