Invasive Mole

Invasive mole (chorioadenoma destruens) is a form of gestational trophoblastic neoplasia in which hydatidiform mole tissue with hydropic villi invades the myometrium and sometimes the parametrium, vessels or distant sites. It arises almost always from a complete mole (about 15% of complete moles progress; 1 to 5% of partial moles) and accounts for most post-molar neoplasia. Invasive moles are highly chemosensitive.

Metastases (most often lung and vagina) are usually self-limiting but can occur, with a low rate of progression to fatal disease. Histologically, hydropic villi with trophoblastic hyperplasia penetrate the myometrium, unlike choriocarcinoma, which lacks villi.

• Persistent or recurrent vaginal bleeding after evacuation of a mole, with hCG that fails to normalise
• Enlarged, boggy uterus; theca lutein ovarian cysts
• Myometrial perforation with intraperitoneal haemorrhage (abdominal pain, shock)
• Haemoptysis, dyspnoea or neurological signs from metastases
• Pulmonary hypertension and respiratory distress from trophoblastic embolisation in severe cases

• Serum hCG meeting the post-molar criteria: plateau over 3 weeks, rise above 10% over 2 weeks, or persistence at 6 months
• Pelvic ultrasound with colour Doppler: heterogeneous, vascular myometrial lesion with anechoic spaces and low resistance flow; MRI for local extent
• Staging: chest radiograph, CT chest and abdomen, and MRI brain if there are lung metastases
• Histology is rarely obtained, and tissue is not needed to start treatment
• Distinguish from retained products, a new pregnancy, phantom hCG (false positive: confirm with urine hCG and heterophile antibody blocking tubes) and quiescent disease (low stable hCG with no progression)

Invasive mole usually scores 6 or less, so low risk treatment applies:

• Methotrexate 50 mg IM on days 1, 3, 5 and 7 with folinic acid 15 mg orally on days 2, 4, 6 and 8, repeated every 14 days; or methotrexate 0.4 mg/kg IV (maximum 25 mg) daily for 5 days every 2 weeks; or actinomycin D 1.25 mg/m2 IV every 2 weeks (or 10 to 12 micrograms/kg daily for 5 days)
• Continue 2 to 3 cycles after the first normal hCG
• Weekly hCG, with full blood count and liver and renal function before each course
• Monitor toxicity: mucositis, myelosuppression, hepatitis, pleuritis and pneumonitis (methotrexate)
• Hysterectomy for women who have completed their families, for heavy uncontrolled bleeding, uterine perforation, or chemoresistant localised disease
• Embolisation or surgery for life threatening bleeding
• High risk features (score 7 or more, brain or liver metastases, long interval from the pregnancy) need EMA-CO: etoposide, actinomycin D and methotrexate with folinic acid rescue on days 1 and 2, then cyclophosphamide and vincristine on day 8, every 2 weeks
• Follow up: hCG monthly for 12 months after normalisation, reliable contraception, then ultrasound and hCG in future pregnancies at 6 to 8 weeks and 6 weeks postpartum
• Prognosis: cure close to 100%, and fertility is generally preserved