A case of pulmonary choriocarcinoma metastasis with unusual FDG-PET and CT findings: correlation with pathology

A 26-year-old female who had had a hydatidiform mole at 20 years of age showed high levels of serum human chorionic gonadotropin. Because pelvic ultrasound did not show any gestational sac in her uterus, she was suspected to have had an extrauterine pregnancy and a spontaneous abortion. About 6 months later, a pulmonary nodule in the patient’s right upper lung field was found on a routine chest X-ray film. Contrast- enhanced CT scans revealed a solitary lobulated nodule 2.0 × 1.3 × 3.0 cm in diameter in the S2 segment of the right lung. CT suggested a vessel malformation. Positron emission tomography using 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG-PET) was performed and showed weak FDG accumulation (SUVmax = 2.0) in the nodule, which did not positively indicate malignancy. Because a follow-up CT showed a rapid increase in the size of the nodule, partial resection of S2 segment in the right upper lobe was performed. The histopathological diagnosis was a metastasis from choriocarcinoma. The tumor consisted largely of necrosis and hemorrhage, and it was considered to be a major cause of the unusual FDG-PET and CT findings.