Placenta
Gestational trophoblastic disease
Complete mole

Author: Sonali Lanjewar, M.D., MBBS (see Authors page)
Editor: Raavi Gupta, M.D.

Revised: 27 April 2017, last major update March 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed search: complete mole [title]

Cite this page: Complete mole. PathologyOutlines.com website. http://pathologyoutlines.com/topic/placentacompletemole.html. Accessed June 24th, 2017.
Definition / general
  • A proliferative disorder of the placenta, resulting in villous hydrops and trophoblastic hyperplasia without embryonic development
  • Diploid paternal only genome
  • Ultrasonography shows characteristic snow storm appearance
  • Patients typically present with abnormal ultrasound, vaginal bleeding or a missed abortion
  • Trophoblastic neoplasia (invasive mole or choriocarcinoma) follows complete mole in 15% - 20% of cases (Am J Obstet Gynecol 1978;131:665, J Reprod Med 1991;36:40, J Reprod Med 1998;43:21, Obstet Gynecol 1992;79:403)
Epidemiology
  • Incidence of 1 in 2000 deliveries in the United States
  • Reported incidences are higher in Mexico (1:200) and in Southeast Asian countries (Philippines: 1:173; India: 1:160; Taiwan: 1:125; and Indonesia: 1:82) (Am J Obstet Gynecol 1964;90:308, Ann N Y Acad Sci 1959;80:178)
  • Extremes of age (< 20 and > 40 years) and previous history of mole
  • Dietary deficiency of vitamin A
Pathophysiology
  • 90% of complete moles are 46 XX, arising from duplication of the chromosomes of a haploid sperm after fertilization of an egg with inactive or absent maternal chromosomes
  • 10% of cases are 46 XY as a result of fertilization of an empty ovum by 2 sperm (dispermy)
  • Rarely tetraploid
Clinical features
  • Vaginal bleeding with passage of grape like vesicles is a common presentation (J Prenat Med 2009;3:15)
  • Disproportionately large uterus for the stage of pregnancy
  • Increasing serum hCG levels after the 14th week, as opposed to the drop typically seen in the course of normal gestation
  • Evidence of toxemia of pregnancy (hypertension, edema, albuminuria) typically during the early stages of the pregnancy
  • Rarely, hyperthyroidism may develop
Radiology description
Radiology images

Images hosted on other servers:

Characteristic vesicular pattern of multiple echoes,
holes within placental mass and no fetus

Laboratory
Prognostic factors
  • Patients with evidence of marked trophoblastic growth such as preevacuation hCG level of 100,000 mIU/mL, excessive uterine growth (20 week size) and theca lutein cysts 6 cm in diameter have 40% incidence of postmolar gestational trophoblastic disease, compared to 4% for those without any of these signs
  • Other factors that increase the risk of post molar gestational trophoblastic neoplasia include age > 40 years, repeat molar pregnancies, aneuploid mole, toxemia, hyperthyroidism and trophoblastic embolization (Am J Obstet Gynecol 2010;203:531, N Engl J Med 2009;360:1639)
Treatment
  • Suction evacuation with curettage
Gross description
  • Bulky, bloody tissue with hydropic changes in all villi which appear as semitransparent vesicles of variable size
  • Classically described as "bunch of grapes," the individual vesicles measure anywhere from 1 to 30 mm in diameter and the total weight is usually over 200 g
  • Normal placental structures or fetal parts are absent
  • Early complete moles may have not have gross evidence of abnormal villi
Gross images

Images hosted on other servers:

Grape-like villi

Complete mole with no embryo / fetus

Microscopic (histologic) description
  • Diffuse villous enlargement with marked hydropic changes
  • Cistern formation and marked trophoblastic hyperplasia usually in a circumferential pattern
  • Remarkable cytologic atypia is almost always present
  • Mitosis is common
  • Presence of exaggerated placental site
  • The distended core of the villus is traversed by widely separated, broken strands of fibrillar material ('cistern' formation)
  • The stromal changes of molar villi, which include stromal mucin and stromal nuclear debris (apoptosis), appear very early and represent a diagnostic clue
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Sonali Lanjewar M.D., MBBS



Images hosted on other servers:

Villus distended with stromal fluid & cistern formation

Atypical trophoblastic proliferation with chorionic villi

Various images

Positive stains
Negative stains
Molecular / cytogenetics description
  • Ploidy analysis is a useful adjunct in diagnosis
  • Molecular analysis with restriction fragment length polymorphism (RFLP), variable number tandem repeat (VNTR) and microsatellite analysis determine the genetic origin of the hydatidiform mole and can be extremely useful for difficult cases (Mod Pathol 2004;17:40)
  • Novel missense NLRP7 gene mutations on chromosome 19q identified in cases of familial clusters of biparental complete hydatidiform moles (J Med Genet 2009;46:569)
Differential diagnosis
  • Partial mole: fetal or embryonic tissue always present, chorionic villi with focal edema, scalloping and prominent stromal trophoblastic inclusions, a functioning villous circulation, focal trophoblastic hyperplasia and minimal atypia
  • Spontaneous hydropic abortion: polarized trophoblastic proliferation, no trophoblast atypia, less edema and no central cistern formation
Board review question #1
Most common karyotype in complete mole is:
  1. 45XX
  2. 46XX
  3. 46XY
  4. 47XXY
Board review answer #1
B. 46XX