Placenta
Gestational trophoblastic disease
Molar pregnancies
Invasive hydatidiform mole
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PubMed Search: Invasive hydatidiform mole[title]
Table of Contents
Essential features | Prognostic factors | Case reports | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Differential diagnosis | Board review style question #1 | Board review style answer #1Cite this page: Lanjewar S, Gupta R. Invasive hydatidiform mole. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/placentainvasivemole.html. Accessed May 30th, 2023.
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
- 40 year old woman with metastasizing invasive hydatidiform mole (Eur J Gynaecol Oncol 2005;26:158)
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
Contributed by Sonali Lanjewar, M.D., M.B.B.S.
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 style question #1
Which of the following is true of invasive mole?
- hCG levels usually normalize after molar resection, then rise again as mole becomes invasive
- It is characterized by an atypical biphasic trophoblastic population and absence of chorionic villi
- It is a rare type of persistent gestational trophoblastic disease
- Vascular invasion, both in the uterus and in metastatic sites, is common
Board review style answer #1
D. Vascular invasion, both in the uterus and in metastatic sites, is common
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Reference: Invasive hydatidiform mole
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