Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Radiology images | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Virtual slides | Positive stains | Negative stains | Sample pathology report | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Sheikh FN, Gupta R, Lanjewar S. Invasive hydatidiform mole. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/placentainvasivemole.html. Accessed March 28th, 2024.
Definition / general
- Invasive hydatidiform mole is a hydatidiform mole that has invaded the myometrium / uterine vessels or is present in extrauterine sites (metastatic hydatidiform mole)
Essential features
- Most common form of persistent gestational trophoblastic disease after persistent hydatidiform mole
- Defined as molar gestation invading the uterine wall, vessels or extrauterine sites
- Extrauterine sites include vaginal / pelvic wall, lungs, vulva
- Most commonly results from complete hydatidiform mole, presenting with persistently elevated human chorionic gonadotropin (hCG) after primary molar evacuation
- Rarely diagnosed on imaging prior to evacuation
- Chemotherapy is highly effective with a cure rate of > 80% (Int J Gynecol Pathol 2016;35:134)
Terminology
- Invasive mole
ICD coding
- ICD-O: 9100/1 - invasive hydatidiform mole
Epidemiology
- After persistent hydatidiform mole, invasive / metastatic hydatidiform mole is the most common form of persistent gestational trophoblastic disease
- Incidence of invasive / metastatic hydatidiform mole is 6 - 10 times higher than choriocarcinoma
- Reference: Kurman: Blaustein Pathology of the Female Genital Tract, 7th Edition, 2019
Sites
- Uterus
- Extrauterine sites: vaginal wall / pelvis (most common), vulva, lungs (Kurman: Blaustein Pathology of the Female Genital Tract, 7th Edition, 2019)
Pathophysiology
- Unknown at this time
Etiology
- Most commonly develops from complete hydatidiform moles (Int J Gynecol Pathol 2016;35:134)
- Rarely seen after a partial mole (Curr Oncol Rep 2014;16:408)
Clinical features
- Vaginal bleeding with persistent serum human chorionic gonadotropin (hCG) after evacuation of a hydatidiform mole is the characteristic presentation (Rev Bras Ginecol Obstet 2015;37:42)
Diagnosis
- Pelvic imaging but can rarely be diagnosed before evacuation
- Uterine evacuation / resection
Laboratory
- Persistently high hCG levels after evacuation of a hydatidiform mole
Radiology description
- It is difficult to differentiate an invasive mole from other forms of gestational trophoblastic disease on imaging
- Pelvic ultrasound
- Echogenic vascular mass invading the myometrium
- High velocity and low impedance flow on color Doppler interrogation
- Pelvic magnetic resonance imaging (MRI)
- Often appears as a poorly defined mass that deeply invades the myometrium
- Complete or partial disruption of the junctional zone may also be seen
- Reference: Radiopaedia: Invasive Mole [Accessed 12 May 2023]
Case reports
- 31 year old woman presented with abdominal pain and scanty vaginal bleeding 53 days postabortion (Front Surg 2022;8:798640)
- 36 year old primigravida woman presented with vaginal bleeding and hCG elevation after removal of a complete hydatidiform mole (Am J Case Rep 2021;22:e931156)
- 41 year old woman who had been pregnant 3 times, had 2 deliveries after 24 weeks gestation and had 1 abortion (G3P2Ab1) presented 2 months after curettage of molar pregnancy with vaginal bleeding and acute abdomen (J Reprod Infertil 2017;18:205)
Treatment
- Chemotherapy has a cure rate of > 80% (Int J Gynecol Pathol 2016;35:134)
Gross description
- Erosive and hemorrhagic lesion
- Superficial or complete invasion of the myometrium that can perforate the uterus and involve periuterine structures
- Hydropic villi may be seen
- Reference: Kurman: Blaustein Pathology of the Female Genital Tract, 7th Edition, 2019
Microscopic (histologic) description
- Presence of molar villi with associated trophoblasts in the myometrium, uterine vessels or extrauterine sites is a diagnostic feature
- Typically, the morphologic characteristics of complete (most common) or partial mole are seen in the invasive component; villi are usually less hydropic but can also show prominent hydropic changes with increased trophoblast hyperplasia
- Metastatic hydatidiform moles are most commonly complete hydatidiform moles in extrauterine locations
- Reference: Kurman: Blaustein Pathology of the Female Genital Tract, 7th Edition, 2019
Microscopic (histologic) images
Positive stains
- Intact nuclear p57 expression in the villous cytotrophoblast and villous stromal cells in invasive hydatidiform moles associated with partial moles
Negative stains
- Loss of nuclear p57 expression in the villous cytotrophoblast and villous stromal cells in invasive complete hydatidiform mole
Sample pathology report
- Uterus, hysterectomy:
- Invasive hydatidiform mole (see comment)
- Comment: Chorionic villi are seen invading the myometrium.
Differential diagnosis
- Choriocarcinoma:
- Also presents with high hCG
- Has more striking cytologic atypia and proliferation in addition to a biphasic pattern of atypical syncytiotrophoblasts and cytotrophoblasts
- 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
- Villi do not show hydropic changes and lack trophoblastic hyperplasia and atypia
- Seen in term placenta whereas molar pregnancies are characteristically seen in first trimester
Additional references
Board review style question #1
Board review style answer #1
B. Pelvis / vaginal wall. The pelvis / vaginal wall is the most common site for metastatic hydatidiform moles. Answers D and A are incorrect because vulva and lungs are the next most common sites. Answer C is incorrect because metastatic invasive hydatidiform moles are not usually seen in the peritoneal cavity.
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Reference: Invasive hydatidiform mole
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Reference: Invasive hydatidiform mole
Board review style question #2
Which of the following is true about invasive hydatidiform mole?
- Grossly presents as a mass-like lesion
- It is a rare type of persistent gestational trophoblastic disease
- Presents as a persistent elevation of hCG after primary evacuation of a hydatidiform mole
- They can usually be diagnosed by imaging prior to removal
Board review style answer #2
C. Presents as a persistent elevation of hCG after primary evacuation of a hydatidiform mole. In invasive / metastatic hydatidiform moles, hCG levels are persistently high despite the evacuation of the primary molar pregnancy. Answer A is incorrect because invasive hydatidiform moles present as an erosive, hemorrhagic lesion on gross examination. Answer B is incorrect because invasive hydatidiform moles are second only to primary hydatidiform moles in incidence. Answer D is incorrect because in most cases, imaging is not helpful in its diagnosis.
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Reference: Invasive hydatidiform mole
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Reference: Invasive hydatidiform mole