its incidence is one in 5333 tubal pregnancies and one in 1.6 million normal intrauterine pregnancies . to our knowledge , a 46-year - old woman , gravida 4 , para 3 , was admitted for abdominal pain . transvaginal sonography showed an empty uterus with a thin endometrium and a 3  cm intramural echogenic mass on the left side of the fundus . there was neither fluid in the douglas pouch , nor adnexal masses nor  ring of fire  signs . human chorionic gonadotropin ( hcg ) was at 6320  mui / ml . these findings were consistent with ectopic interstitial pregnancy . according to the department 's protocol , the patient received a single dose of methotrexate . hcg decreased to 3010  mui / ml after one week , then raised to 7020  mui / ml two weeks later . therefore , the patient underwent a laparoscopy . a 3  cm mass located on the left side of the uterine fundus thus , a monthly monitoring of plasmatic hcg level was decided till its negativity . however , earlier to her first appointment , the patient presented in the emergency room with severe acute pelvic pain and vaginal bleeding . ultra sonography revealed a hyper echoic intrauterine mass and hcg titer was very high ( 4,000,000  mui / ml ) suggestive for a persistent trophoblastic disease . histological examination revealed a proliferation of atypical trophoblastic cells , both syncytiotrophoblastic and cytotrophoblastic cells with numerous mitoses . the stroma was hemorrhagic and the tumor cells infiltration is limited to the myometrial wall . the patient was followed by hcg test weekly in the first month , then monthly during the first year . j curve  and younger < 18 year old and women > 40 have higher rates . although the tumor may arise from any type of prior gestational events as normal pregnancy or spontaneous abortion , it more frequently complicates hydatidiform mole regardless of its intrauterine or ectopic location . the development of the tumor varies between 5 weeks and 15 years after gestation or even after menopause . its association with ectopic pregnancy is extremely rare and in general with aggressive behavior . indeed , only 0.764% of choriocarcinomas developed in ectopic location . its specific occurrence in interstitial pregnancy is exceptional with , in our knowledge , three cases being reported in the literature including the present one . the diagnosis of primary extra - uterine choriocarcinoma is challenging because the clinical symptoms are often nonspecific and can mimic hemorrhagic ovarian cyst , tubo - ovarian abscess , ovarian torsion , and ectopic pregnancy . the frequency of metastatic disease with resultant increased morbidity and mortality is related to the delayed diagnosis . the typical sonographic appearance of intra - uterine choriocarcinoma is a large echogenic irregular mass occupying the uterine cavity , hyper vascularized in color - flow doppler . serial measurement of hcg level was the most useful marker of diagnosis and follow up . when nonmetastatic choriocarcinoma occurs in young patients who desire to preserve their fertility , it should be treated by local resection of the tumor followed by chemotherapy . at the new england trophoblastic disease center , all the women with tubal choriocarcinoma ( 6/6 ) achieved complete remission with chemotherapy even those with metastases ( 4/6 ) . the two cases of choriocarcinoma arising in an interstitial pregnancy reported were also successfully treated with chemotherapy based on methotrexate . the increasing tendency to treat ectopic pregnancy by conservative management suggests the crucial role of pathological examination associated with hcg level follow up , not only to diagnose persistent ectopic pregnancy but also to avoid missing malignant trophoblastic disease . mohamed salah rhim was involved in the analysis and interpretation of data and drafting the article . mohamed tahar yacoubi and hedi khairi gave final approval of the version to be submitted .
highlightschoriocarcinoma is a highly malignant trophoblastic neoplasm . 
 its association with ectopic pregnancy is very rare and aggressive.clinical diagnosis of interstitial choriocarcinomas is difficult , since it is rare and manifested by non - specific symptoms.imaging findings are also not helpful in ectopic location.monitoring of hcg level was the most useful marker of diagnosis and follow up.pathology is the only tool of the diagnosis especially with the trend of treatment of ectopic pregnancy by conservative surgery .