Choriocarcinoma is a rare malignant neoplasm that develops in the placental chorionic epithelial tissue niche. It is most commonly due to malignant transformation of hydatidiform moles, although it can develop following term pregnancy, spontaneous abortion, and even ectopic pregnancy . It is known for a rapid hematogenous spread to multiple organs . Approximately 30 % of cases of choriocarcinoma have metastatic disease at the time of diagnosis. Lungs (80%) are the most common site of metastasis, followed by the vagina (30%), liver (10%), and brain (3-28%). However, skin, gastrointestinal tract, kidney, breast, and bones are infrequent sites [7-9]. The clinical signs of choriocarcinoma are so much varied that every case may be one of its kinds and thus can be a diagnostic challenge.
In our case, the patient presented with metastasis to the lung, lumbar vertebrae, epidural space, and adrenal gland. The lung has been described as the most common site for choriocarcinoma metastasis . However, metastasis to the adrenal gland, lumbar vertebrae, and epidural space is extremely rare. Only 5 cases of metastatic choriocarcinoma in the lumbar and/ or epidural space have been reported thus far in the recent 20 years [3-5, 10, 11], and metastasis to adrenal gland has not been reported. Although we did not have any direct anatomopathological evidence related to the adrenal gland, image findings of abdominal CT and the reduction of the lesion after chemotherapy suggested that such metastases were present.
In our case, MRI of the lumbar vertebrae revealed a nodular lesion in the anterior epidural space from L3 to L4 vertebral level with heterogeneous low intensity on T1WI and T2WI. There was also an abnormal signal in the L4 vertebral body with low intensity on T1WI and high intensity on T2WI. The L4 vertebral body was not severely damaged, and the shape of the pedicle was standard. But its architecture of the cortical bone in the anterior epidural space was discontinuous, which can be seen on CT and MRI of lumbar vertebrae. Combined with these findings, our initial diagnosis was a tumor or hematoma, while the patient had an ectopic pregnancy. To quickly recover the muscle strength of the patient's lower limbs and improve symptoms of dysuria, surgery of the lumbar spinal canal decompression and mass resection was required. However, the profuse intraspinal bleeding interrupted the operation, which also confirmed the high possibility of malignancy because the bleeding could be caused by the rupture of blood vessels that feed malignant tumors.
Because of the affinity of trophoblast cells for blood vessels, metastases of choriocarcinoma often develop early and are mostly hematogenous. Due to the inherent ability of trophoblast cells to erode the walls of blood vessels and the fact that choriocarcinoma can pass through fragile blood vessel walls, the symptoms of metastases are frequently hemorrhagic. In our case, the patient had elevated β-HCG, but no pregnancy capsule was found in the uterus. We first considered the possibility of ectopic pregnancy but ignored the possibility of a trophoblast tumor. With the findings of tumors in both lungs and adrenal gland, we preferred to use metastatic carcinoma to explain all the results of the patient. Nonetheless, the exact location of the primary lesion was still unclear.