partial hydatidiform mole

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 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.

Villi have only paternal DNA, so they don’t stain for p57kip2. However, decidua and intermediate trophoblasts will still stain for p57, since they are maternal tissues.

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.

Synopsis

 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.

Associations

 constitutional triploidy

Immunochemistry

 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.

Molecular genotyping

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.

Differential diagnosis

 hydropic abortion

 complete mole

• 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.

See also

 gestational trophoblastic diseases
 hydatiform mole

References

 Diagnostic Reproducibility of Hydatidiform Moles: Ancillary Techniques (p57 Immunohistochemistry and Molecular Genotyping) Improve Morphologic Diagnosis. Vang R, Gupta M, Wu LS, Yemelyanova AV, Kurman RJ, Murphy KM, Descipio C, Ronnett BM. Am J Surg Pathol. 2012 Mar;36(3):443-53.PMID: 22245958

 Diandric Triploid Hydatidiform Mole With Loss of Maternal Chromosome 11. Descipio C, Haley L, Beierl K, Pandit AP, Murphy KM, Ronnett BM. Am J Surg Pathol. 2011 Aug 29. PMID: 21881485

 Popiolek DA, Yee H, Mittal K, Chiriboga L, Prinz MK, Caragine TA, Budimlija ZM. Multiplex short tandem repeat DNA analysis confirms the accuracy of p57(KIP2) immunostaining in the diagnosis of complete hydatidiform mole. Hum Pathol. 2006 Nov;37(11):1426-34. PMID: 16949913

 Murdoch S, Djuric U, Mazhar B, Seoud M, Khan R, Kuick R, Bagga R, Kircheisen R, Ao A, Ratti B, Hanash S, Rouleau GA, Slim R. Mutations in NALP7 cause recurrent hydatidiform moles and reproductive wastage in humans. Nat Genet. 2006 Feb 5; PMID: 16462743

 Romaguera RL, Rodriguez MM, Bruce JH, Zuluaga T, Viciana A, Penalver MA, Mehrdad N. Molar gestations and hydropic abortions differentiated by p57 immunostaining. Fetal Pediatr Pathol. 2004 Mar-Jun;23(2-3):181-90. PMID: 15768863

 Jun SY, Ro JY, Kim KR. p57kip2 is useful in the classification and differential diagnosis of complete and partial hydatidiform moles. Histopathology. 2003 Jul;43(1):17-25. PMID: 12823708