partial hydatidiform mole
Wednesday 10 April 2013
Partial Hydatidiform Mole by Ed Euthman
Definition: Hydatiform mole is a gestational trophoblastic disorder.
Cases of PARTIAL MOLE (PHM) are triploid and usually result from fertilization of an ovum by 2 sperms, although fertilization by a single diploid sperm cannot be excluded.
Partial mole has fetal parts, such as nucleated fetal RBCs in the villi.
Partial mole / incomplete mole is usually triploid, 69 XXX or 69 XXY, and has an extra set of paternal chromosomes (1 maternal, 2 paternal).
Histologically, it has normal and abnormal villi, villous scalloping, focal trophoblastic hyperplasia, and may have fetal RBCs. The uterus is usually small for dates. p57 stains only maternal DNA. due to paternal imprinting on chromosome 11. p57 stains villous stroma and cytotrophoblasts.
Since incomplete moles have maternal DNA, and complete moles do not, p57 is positive in incomplete moles. Mnemonic: Partial, fetal Parts, P57 positive partial.
partial hydatiform mole
- With a partial mole, fetal tissue is often present. Fetal erythrocytes and vessels in the villi are a common finding.
- The chromosomal complement is 69,XXX or 69,XXY. This results from fertilization of a haploid ovum and duplication of the paternal haploid chromosomes or from dispermy.
- Tetraploidy may also be encountered. As in a complete mole, hyperplastic trophoblastic tissue and swelling of the chorionic villi occur.
With a partial mole, fetal tissue is often present. Fetal erythrocytes and vessels in the villi are a common finding.
The chromosomal complement is 69,XXX or 69,XXY. This results from fertilization of a haploid ovum and duplication of the paternal haploid chromosomes or from dispermy.
Tetraploidy may also be encountered.
As in a complete mole, hyperplastic trophoblastic tissue and swelling of the chorionic villi occur.
p57KIP2 (CDKN1C) expression in molar pregnancy
- Negative p57KIP2 (CDKN1C) immunoreactivity (paternally imprinted, maternally expressed gene) is in perfect concordance with the androgenetic origin of molar pregnancies proven by DNA polymorphism. (15971478)
- p57KIP2 (CDKN1C) immunoreactivity, which can be performed in routine pathologic examinations, is a diagnostic tool to differentiate androgenetic complete moles from biparental conceptuses. (15971478)
- The p57KIP2 gene is paternally imprinted and is expressed from the maternal allele, and the lack of its protein product, as detected by IHC, has been documented in CHM (because CHMs lack maternal genomic DNA).
- In contrast, its mimics express p57KIP2, which serves as a surrogate marker for maternal DNA.
Distinction of hydatidiform moles (HMs) from nonmolar specimens (NMs) and subclassification of HMs as complete hydatidiform moles (CHMs) and partial hydatidiform moles (PHMs) are important for clinical practice and investigational studies.
Molecular genotyping can distinguish these entities by discerning androgenetic diploidy, diandric triploidy, and biparental diploidy to diagnose CHMs, PHMs, and NMs, respectively.
- Complete mole is diploid, 46 XX or 46 XY, and has only paternal chromosomes.
- Histologically it has abnormal, enlarged villi with large cisterns, diffuse trophoblastic proliferation, and no fetal parts.
- Patients tend to have a large uterus for dates.
- p57 stains maternal DNA only due to paternal imprinting.
- p57 will STILL BE POSITIVE in decidua and intermediate trophoblasts, since these are the mother’s tissue.
- So, just because there is some staining for p57 on the slide, don’t jump to a diagnosis of partial mole.
- You must look at the villi.
- p57 will not be positive in the abnormal villi, since there is only paternal DNA.
- Complete mole is 46 XX or XY, paternal only.
- Partial mole is usually triploid, 69 XXY or 69 XXX with 1 maternal and 2 paternal sets of chromosomes.
- Complete mole has Cisterns, complete (diffuse) trophoblast proliferation, completely lacks maternal DNA, and completely lacks p57. Partial is P57 Positive.
- Mnemonic: Complete, Cisterns, Completely paternal, Complete (diffuse) trophoblastic proliferation. Completely lacks p57.
gestational trophoblastic diseases
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