You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
choriocarcinoma presenting as a pulmonary embolism is extremely rare . because of the rarity of tumors of the pulmonary arteries , these tumors
this paper reports a case of a patient with a choriocarcinoma presenting as a massive pulmonary embolism ( pe ) , who required venoarterial ( va ) extracorporeal membrane oxygenation ( ecmo ) support for bridging to a surgical embolectomy and chemotherapy .
a 22-year - old woman ( gravida 1 , para 0 ) presented at the local hospital complaining of dyspnea .
her menstrual history revealed that she had experienced menarche at age 14 , irregular cycles in the past , and occasional vaginal spotting in last two cycles .
she was treated for pulmonary tuberculosis and pneumothorax with tuberculosis medications and the insertion of a chest tube ; however , her symptoms worsened .
a pulmonary thromboembolism was suspected , and chest enhanced computed tomography ( ct ) showed a filling defect in the left inferior pulmonary artery ( fig .
two weeks after starting treatment with rivaroxaban , the patient presented with aggravated dyspnea and massive hemoptysis and was urgently referred to the emergency department ( ed ) . upon arrival at the ed ,
the patient was afebrile , with a heart rate of 138 beats per minute , blood pressure ( bp ) of 90/80 mm hg , respiratory rate of 18 breaths per minute , and oxygen saturation of 100% in room air .
the chest examination for the breath sounds and auscultation revealed coarse crackles from the right lung and no sounds from the left .
the arterial blood gas levels under oxygen mask inhalation ( 5 l / min ) were as follows : ph , 7.51 ; pao2 , 81 mm hg ; and paco2 , 25 mm hg .
her hemoglobin level was 13.1 g / dl , white blood cell count was 7,520/ml , and platelet count was 273,000/ml .
the d - dimer was 2.72 g / ml , and the troponin level was elevated slightly , at 0.01 ng / ml . her chest radiograph revealed a normal cardiac field , diffuse nodularity in both lung fields , and a pneumothorax with chest tubing in the left lung zone . while repositioning the chest tube into the pneumothorax , she became mentally confused , and the laboratory results showed a partial pressure of oxygen ( po2 ) of 38 mm hg .
she was intubated , started on mechanical ventilation , and admitted to the intensive care unit for further evaluation .
the patient remained hypotensive despite the intravenous fluid boluses that escalated the inotropic infusion with the maximum dose .
an echocardiogram revealed a severe left ventricular systolic dysfunction with an ejection fraction of 29% and a d - shaped left ventricle .
pulmonary angiography was performed and showed a large filling defect in the left pulmonary artery ( fig .
at the site of the main pulmonary artery near its opening to the left pulmonary artery , a whitish tumor embolus was found in the left pulmonary artery .
histologically , the pulmonary tumor embolism specimen revealed a malignancy consistent with choriocarcinoma ( fig .
2 ) . after a diagnosis of choriocarcinoma was made , the serum beta human chorionic gonadotropin ( hcg ) level was measured , and a gynecologic examination was performed .
a metastatic workup revealed no lesions in the liver , spleen , kidney , pelvic cavity , and brain ( international federation of gynecology and obstetrics [ figo ] stage iii , figo prognostic score 6 ) .
although she was under an ecmo insertion state and her platelet level was below 75,000/l , chemotherapy was started with the following conventional regimen after receiving fully informed consent : etoposide , 100 mg / m on days 1 and 2 ; methotrexate , 100 mg / m via intravenous bolus on day 1 and 200 mg / m via intravenous infusion over 12 hours on day 1 ; actinomycin d , 0.5 mg via intravenous bolus on day 1 and 2 ; cyclophosphamide , 600 mg via intravenous infusion on day 8 ; and vincristine , 1.0 mg / m on day 8 ( ema - co ) .
after the initial chemotherapy , her beta hcg level decreased to 2,296 miu / ml , and the ecmo was removed as her heart function was restored .
the second cycle of chemotherapy was postponed because of a poor general condition and grade 4 neutropenia . after a 2-month period of chemotherapy ,
choriocarcinoma is a malignant , gestational trophoblastic neoplasm that can occur after a molar hydatidiform mole , ectopic pregnancy , abortion , and even normal pregnancy .
choriocarcinomas spread hematogenously to the lungs , resulting in pe , pulmonary hypertension , or acute respiratory distress syndrome .
although the prognosis for metastatic gestational choriocarcinoma to the lungs ( stage iii ) is good , the rarity of a pe can result in a misdiagnosis , and the patient might be treated for more common diseases , such as pneumonia and tuberculosis . in the present case
, the patient also was diagnosed incorrectly with tuberculosis and a venous pulmonary thrombosis . in the case of fertile women presenting with dyspnea , cough , and hemoptysis , it is essential to have a suspicion of a tumor embolism .
watanabe et al .   emphasized the importance of considering choriocarcinoma and measuring the serum beta hcg levels when evaluating fertile women presenting with pulmonary emboli or pulmonary artery hypertension .
therefore , it is recommended that the serum beta hcg level be performed as a diagnostic test in women of reproductive age to differentiate the causes of a pe .
patients presenting with massive pe complicated by right ventricular failure and cardiogenic shock have high short - term mortality ( > 25% ) .
the hemodynamic instability hinders a clinical evaluation including chest ct scan and pulmonary angiography . with regard to treatment , urgent
thrombolysis or surgical approach is mandatory ; however , these treatments might be limited because of refractory hypoxia and shock .
va ecmo could be an optional strategy in a patient with a massive pe as a bridge to further diagnostic work - up and therapeutic interventions .
chowdhury et al .   reported the use of va ecmo as an adjunct to thrombolytic therapy for progressive circulatory collapse secondary to a massive acute pe .
as in other cases , the patient remained hypotensive despite intravenous fluid boluses , in which inotropic infusion was escalated escalating to the maximum dose . to perform diagnostic workup and therapeutic interventions , such as embolectomy and pulmonary angiogram ,
ecmo is essential to maintain hemodynamic stability . to the best of the authors knowledge ,
only a few cases of a pulmonary embolectomy to remove tumor emboli from choriocarcinoma have been reported . on the other hand , this is a rare case of a patient with a metastatic gestational choriocarcinoma who presented with a pulmonary artery tumor embolism by employing ecmo and pulmonary embolectomy followed by chemotherapy . according to worku et al . , a patient with lymphoma developed cardiogenic shock at the time of chemotherapy initiation .
ecmo was instituted to restore the hemodynamic stability , and to bridge the patient to chemotherapy until the tumor burden could be reduced effectively . in this study ,
generally , chemotherapy is not recommended routinely in a patient under ecmo because of its adverse effects , such as neutropenia or thrombocytopenia . despite this
, the choriocarcinoma responded very well to the chemotherapeutic agent initiated , and the patient under va ecmo responded positively , with serum beta hcg falling to within the normal levels .
therefore , although the prolonged use of ecmo would increase the risk of morbidity , including thrombotic and hemorrhagic complications , its adequate application allows the patient to achieve benefits as an effective bridging therapy , while minimizing complications .
these results suggest that although metastatic gestational choriocarcinoma is rare , it should be considered in a differential diagnosis of fertile women presenting with a massive pe . in addition , ecmo may be used as an adjunct to bridge to embolectomy and chemotherapy as soon as possible in a patient with hemodynamic instability , because of the potential for a good response of the choriocarcinoma to the chemotherapy .
a 22-year - old woman with a 1-month history of shortness of breath that was treated as a case of tuberculosis and pulmonary embolism was referred to the authors hospital . 
 because of the hemodynamic instability in this patient , venoarterial extracorporeal membrane oxygenation ( ecmo ) was administered in the intensive care unit . 
 she underwent a pulmonary embolectomy for the treatment of progressive circulatory collapse secondary to a pulmonary embolism . 
 the histopathologic result was consistent with a metastatic choriocarcinoma . despite the surgical management , persistent refractory cardiogenic shock occurred . 
 subsequently , the patient was treated with chemotherapy in the presence of ecmo and responded well to chemotherapy . 
 she was discharged after 3 months . 
 this case suggests that metastatic choriocarcinoma should be considered as a differential diagnosis in women of childbearing age presenting with a pulmonary embolism , and ecmo may be beneficial in patients with pulmonary embolism for bridging to surgical embolectomy and chemotherapy .