[1107] Characteristics of Hydatidiform Moles: Analysis of p57 Expression and Molecular Genotyping Data

Natalie Banet, Cheryl DeScipio, Brigitte M Ronnett. Johns Hopkins University, Baltimore, MD

Background: Recent studies have established that p57 immunostaining and molecular genotyping accurately subclassify molar specimens into complete hydatidiform mole (CHM) and partial hydatidiform mole (PHM) and distinguish these from non-molar specimens (NM). Detailed characteristics of a large series analyzed with these techniques have not been reported.
Design: All potentially molar specimens encountered in a large gynecologic pathology practice were analyzed with p57 immunostaining and genotyping. Initially, all specimens were subjected to both analyses; this was later modified to triage cases for genotyping based on p57 results (p57-negative cases diagnosed as CHMs without genotyping; all p57-positive cases genotyped).
Results: 519 cases were categorized as CHM (166), PHM (127), NM (208), and complex (18). Of 166 CHMs, 165 were p57-negative and 1 was p57-positive (due to retained maternal chromosome 11). 95 genotyped CHMs were androgenetic diploid; 81 (85%) were monospermic XX and 14 (15%) were dispermic (12 XY, 2 XX). 8 CHMs were invasive (6 monospermic XX, 2 dispermic XY), including 4 with atypical trophoblastic proliferations consistent with choriocarcinoma (3 monospermic XX, 1 dispermic XY); 2 non-invasive CHMs had atypical trophoblastic proliferations consistent with choriocarcinoma (1 monospermic XX, 1 dispermic XY). Of 127 PHMs, 124 were p57-positive and 2 were p57-negative (due to loss of maternal chromosome 11); 1 was non-reactive (due to degenerative changes). Of these, 122 were diandric triploid and 3 were triandric tetraploid; 2 were morphologically consistent with PHMs but with triploidy of undetemined origin (due to lack of decidual tissue for analysis). Of 122 diandric triploid PHMs, 118 (97%) were dispermic (67 XXY, 44 XXX, 7 XYY) and 4 (3%) were monospermic (3 XXX, 1 XYY); the 3 triandric tetraploid PHMs were at least dispermic (2 XXYY, 1 XXXY). Of 208 NMs, 204 were p57-positive and 1 was p57-negative; 4 were non-reactive. 205 were biparental diploid and 3 were digynic triploid; the p57-negative biparental diploid specimen had abnormal, enlarged villi but no trophoblastic hyperplasia, possibly an early form of Beckwith-Wiedemann syndrome. 18 cases were genotypically complex and included androgenetic/biparental mosaic specimens with discordant p57 expression (analyzed in another study).
Conclusions: CHMs are overwhelmingly p57-negative monospermic androgenetic diploid conceptions whereas PHMs are almost always p57-positive dispermic diandric triploid conceptions. Rare examples with aberrant p57 expression can be correctly classified by genotyping.
Category: Gynecologic & Obstetrics

Monday, March 4, 2013 11:45 AM

Proffered Papers: Section E, Monday Morning

 

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