Placenta
Gestational trophoblastic disease
Invasive mole

Author: Sonali Lanjewar, M.D., MBBS
Editor: Raavi Gupta, M.D.
Editorial Board Member Review: Carlos Parra-Herran, M.D.

Revised: 24 January 2018, last major update December 2017

Copyright: (c) 2002-2018, PathologyOutlines.com, Inc.

PubMed Search: Invasive mole[title]

Cite this page: Lanjewar, S. Invasive mole. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/placentainvasivemole.html. Accessed November 15th, 2018.
Essential features
  • Most common form of persistent or metastatic gestational trophoblastic disease (GTD) after hydatidiform mole; occurs 6 - 10 times more frequently than choriocarcinoma
  • Defined as molar gestation invading myometrium or uterine vessels
  • Commonly presents with vaginal bleeding and persistent elevation of hCG
  • Commonly diagnosed after primary evacuation of complete or partial mole; rarely diagnosed on imaging before molar evacuation
  • Extrauterine spread to lungs, vagina, vulva and broad ligament in 20 - 40% of cases (J Clin Ultrasound 2013;41:113)
  • Rarely spreads to paraspinal soft tissue (Kurman: Blaustein's Pathology of the Female Genital Tract, 6th edition, 2011)
Prognostic factors
  • Chemotherapy is highly effective, with 80% cure rate
Case reports
Gross description
  • Hydropic villi are visible - can be seen extending from endometrium into the myometrium
  • Perforation of uterus can occur
  • In the uterus, commonly seen as an erosive hemorrhagic lesion
Microscopic (histologic) description
  • Abnormal (dysmorphic) chorionic villi and extravillous trophoblast invade myometrium and blood vessels
  • Absence intervening decidua
  • Typically the morphologic characteristics of complete (most common) or partial mole are retained in the invasive component
  • There is marked proliferation of trophoblasts with mild to severe atypia
  • Villi are less hydropic than noninvasive mole
  • In metastatic sites, diagnosis is based on identification of villi, which are usually confined to vessels without tissue invasion
  • Since diagnosis requires the presence of myometrium and vessels invaded by villi, it can only be confirmed pathologically on resection material; biopsy / curettage material usually is insufficient for this diagnosis
Microscopic (histologic) images

Images hosted on PathOut server:

Images contributed by Dr. Sonali Lanjewar:

Villi invading myometrium

Trophoblastic proliferation

Differential diagnosis
  • Choriocarcinoma: both invasive mole and choriocarcinoma present with high hCG
    • Choriocarcinoma has more stricking cytologic atypia and proliferation and has a biphasic pattern of atypical syncytiotrophoblast and cytotrophoblast; it also lacks villi (except In the rare instance of gestational choriocarcinoma)
  • Placenta accreta: normal placenta with villous implants invading into the myometrium without an intervening decidual layer; in contrast to invasive mole, villi in accreta do not show hydropic changes and lack trophoblastic hyperplasia and atypia
Board review question #1
Which of the following is true of invasive mole?

  1. hCG levels usually normalize after molar resection, then rise again as mole becomes invasive
  2. It is characterized by an atypical biphasic trophoblastic population and absence of chorionic villi
  3. It is a rare type of persistent gestational trophoblastic disease
  4. Vascular invasion, both in the uterus and in metastatic sites, is common
Board review answer #1
D. Vascular invasion, both in the uterus and in metastatic sites, is common