Discussion
  The lung is the most common site of metastasis in patients with choriocarcinoma, in which blood borne metastasis often develops early because of the affinity of trophoblast for blood vessels and the majority of metastases go to the lungs (75%). The major form of pulmonary involvement is invariably hematogenous and is usually manifested roentgenographically by multiple parenchymal nodules, and miliary or “snowstorm” opacities. Hemorrhage about the periphery of the metastatic nodules can be seen in choriocarcinoma resulting ill-defined margin. Intratumoral hemorrhage is also developed. In this case, necrotic tumor tissue and blood occupy the central portions of pulmonary metastatic nodules. Less often, tumor embolization occurs when tumor invades the systemic veins and proceeds to the right side of the heart and pulmonary arteries. This entity is distinct from hematogenous dissemination in that there is no proliferation of metastases within extravascular tissues. The majority of patients with nodular metastases are usually asymptomatic, probably due to the predominantly peripheral distribution of lesions, although dyspnea may develop and hemoptysis can occur as a result of intrapulmonary hemorrhage. In contrast, tumor embolization may cause symptoms consistent with acute or subacute cor pulmonale or pulmonary infarction. On occasion, hemorrhagic infarction is developed. Calcification has been noted at the site of successfully treated metastatic choriocarcinoma.

References
1. Green CL, Angtuaco TL, Shah HR, Parmley TH. Gestational trophoblastic disease: a spectrum of radiologic diagnosis. Radiographics 1996; 16: 1371-1384
2. Primack SL, Hartman TE, Lee KS, M?ller NL. Pulmonary nodules and the CT halo sign. Radiology 1994;190:512-515
3. Gildersleeve N Jr, Koo AH, McDonald CJ. Metastatic tumor presenting as intracerebral hemorrhage. Radiology 1977;124:109-112
4. Libshitz, HI, Baber CE, Hammond CB. The pulmonary metastases of choriocarcinoma. Obstet. Gynecol.1977;49:412.