Placenta
Gestational trophoblastic disease
Incomplete / partial mole

Author: Mandolin Ziadie, M.D. (see Authors page)

Revised: 20 October 2017, last major update December 2011

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Incomplete mole[title] OR partial mole[title]

Cite this page: Ziadie, M. Incomplete / partial mole. PathologyOutlines.com website. http://pathologyoutlines.com/topic/placentaincompletemole.html. Accessed November 22nd, 2017.
Definition / general
  • 20% of all moles
  • 9% of spontaneous abortions
  • Triploid or tetraploid, some are trisomy 16
  • Variable percentage (up to 86% in some studies) of triploid abortuses may have histologic features of partial moles (Hum Pathol 1996;27:1018) but many cases are actually due to extra maternal genome (digynic zygotes)
  • Note: not all triploid conceptuses show molar transformation, although most die at age 8 weeks
  • Diandric; contains extra set of paternal chromosomes due to fertilization by two sperm or by a single diploid sperm
  • Diagnosed in second trimester or later
  • Patients have small for date uteri without marked hCG elevation
  • May be associated with toxemia of pregnancy; may present as missed or spontaneous abortion
  • 4 - 12% develop persistent gestational trophoblastic disease; very low risk of choriocarcinoma; invasive mole rare; persistent intrauterine disease may develop
Treatment
  • Closely monitor hCG
  • Chest Xray
Gross description
  • Smaller volume of tissue than complete mole (200 ml or less)
  • Mixture of grossly vesicular and normal villi
  • Fetus / embryo is usually present, although often abnormal (blighted ovum) or with syndactyly of digits 3 and 4 on both hands and feet
Gross images

Images hosted on other servers:

Partial hydatidiform mole

Microscopic (histologic) description
  • Mixture of edematous villi similar to complete mole and relatively normal villi (Hum Pathol 2000;31:914, Hum Pathol 1981;12:1016)
  • Less conspicuous central cistern formation (internal clefting)
  • Mild focal trophoblast hyperplasia without atypia
  • Villous scalloping (invaginations of trophoblast tissue into villous stroma, appears circular in cross section and resembles coast of Norway or inclusions)
  • Smaller villi usually have stromal fibrosis
  • Villi have vessels with nucleated RBCs if fetal development present
Microscopic (histologic) images

Images hosted on other servers:

Minimal trophoblastic proliferation; some have hydropic villi

Positive stains
Molecular / cytogenetics description
Differential diagnosis