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A Reappraisal of the Incidence of Placental Hydatidiform Mole Using Selective Molecular Genotyping
  1. Terence J. Colgan, MD*,
  2. Martin C. Chang, MD, PhD,
  3. Shabin Nanji, MBB Chir, MD and
  4. Elena Kolomietz, PhD
  1. *Section of Gynecological Pathology, Department of Pathology and Laboratory Medicine, Mount Sinai Hospital,
  2. Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, and
  3. Division of Diagnostic Medical Genetics, Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, Canada.
  1. Address correspondence reprint requests to Terence Colgan, MD, Mount Sinai Hospital, Room 6-502, 600 University Ave, Toronto, Ontario, Canada, M5G 1X5. E-mail:


Objective Reports on the incidence of hydatidiform mole (HM) have varied depending on study population and methodology. This institutional-based study was undertaken to identify the incidence of HM in a modern obstetric practice using advanced laboratory diagnostic techniques.

Methods A retrospective review of consecutive hospital cases of HM was conducted for a 27-month period. Pathologic diagnoses of partial mole (PM) and complete mole (CM) were based on histopathologic assessment and selective use of p57 immunohistochemistry and molecular genotyping (MG) using formalin-fixed paraffin-embedded tissues.

Results During the study period, 14,944 obstetric deliveries took place at our institution. Forty-nine cases of HM (18 CMs, 31 PMs) were identified. Histopathology with the selective use of p57 immunohistochemistry was used in 25 of 49 HMs (18 CMs, 7 PMs). Histopathologic features were equivocal in the remaining cases (24/49 cases), and adjunctive MG was performed; all were PMs. The incidence of HM was 3.3/1000 deliveries. Partial mole was more prevalent with a CM (PM ratio, 1:1.72).

Conclusions Our observed incidence of HM is greater than previous studies and is attributable to improved detection of PM cases. Molecular genotyping and cytogenetic evidence indicate that CM is almost half as common as PM. This ratio may be useful in benchmarking laboratory diagnosis and HM registries.

  • Hydatidiform mole
  • Gestational trophoblastic disease
  • Molecular genotyping
  • Disease incidence

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  • This study received no extramural funding and was supported by the Department of Pathology and Laboratory Medicine, Mount Sinai Hospital.

  • The authors declare no conflicts of interest.

  • Postscript: Following the submission of this manuscript, a recent population-based study from the Netherlands reported a HM incidence rate of only 1.32 per 1000 deliveries. Eysbouts YK, Bulten J, Ottevanger PB, et al. Trends in the incidence for gestational trophoblastic disease over the last 20 years in a population-based study. Gynecol Oncol 2016; 140:70–5.