[1011] Comparison of Fluorescent In Situ Hybridization (FISH), p57 Immunohistochemical (IHC) Staining and Flow Cytometry (FC) in the Work-Up of Suspected Molar Gestation.

Nyasha Bullock, Laila Mnayer, Elizabeth Tambling, Joseph DiGiuseppe, Margaret Assaad, Srini Mandavilli. Hartford Hospital, CT

Background: Distinguishing early complete hydatidiform mole (CHM), partial hydatidiform mole (PHM) and hydropic abortus (HA) can occasionally be difficult on a morphologic basis. A variety of ancillary methods (p57 IHC and DNA ploidy analysis by Flow Cytometry and more recently molecular techniques including FISH and molecular genotyping) are utilized to aid in difficult cases. There is limited literature comparing these various methodologies on a single study set of products of conception (POC) cases. The aim of this study was to evaluate the utility of FISH compared to relatively well-established p57 IHC and FC, including accuracy and turnaround time in a community hospital setting.
Design: Thirty-two cases of products of conception (POC) were retrieved from the pathology files at our institution for the time period January 2010-August 2010. All of these cases had morphologic findings that prompted further work-up with either p57 IHC (1:1000; Thermo Fisher, Fremont California), DNA ploidy by flow cytometry and/ or FISH. We retrospectively performed IHC and FISH on all cases to complete the cohort. P57 IHC was considered positive when villous trophoblasts and stromal cells showed strong positivity. FISH procedure utilized 4 centromeric probes (chromosomes 1, 17, X and Y; Abbot Molecular). Trisomy 1 and 17 is incompatible with fetal implantation, unless it is part of a triploidy and this was the rationale in picking these FISH probes over others. X and Y chromosome probes in addition to confirming the findings, allow detection of the sex chromosome complement. DNA ploidy by FC was performed using flow cytometer (BD FACSCanto II) following DNA extraction of paraffin embedded material.

Final Diagnosis (# of cases)Flow CytometryP57 positivity in villous trophoblastFISH
HA (20)Diploid (17); Tetraploid (3)PositiveDiploid
PM (10)TriploidPositiveTriploid
CHM (2)DiploidNegativeDiploid
Turnaround time8 days2 days2-3 days

Conclusions: 1. FISH offers the following advantages over FC:
a. Less hands on technical time,
b. Is less susceptible to artifacts of cellular aggregates that can cause misclassification of a diploid case as tetraploid (3/20 cases) by FC,
c. Is more sensitive because ploidy is evaluated in visualized cells, and hence maternal tissue contaminating artifact can be avoided,
d. Shorter turn around time.
2. The combination of FISH and IHC is superior to the previously used combination of FC and IHC.
Category: Gynecologic & Obstetrics

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 127, Wednesday Morning


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