GTDs encompass a heterogeneous group of neoplastic disorders that arise from the trophoblastic epithelium of the placenta and they are characterized by a distinct tumor marker (β-HCG)1,7,8,11,12,17,20,22,23,25)
. GTDs are conventionally classified into at least five distinct groups on the basis of their histopathologic, cytogenetic, and clinical features12)
. They are complete and partial hydatidiform mole, invasive mole, choriocarcinoma, placental site trophoblastic tumor and miscellaneous trophoblastic lesions. Choriocarcinoma is a rare, highly malignant neoplasm of a trophoblastic origin among the GTDs. This tumor is known for its association with molar pregnancy, a rapid hematogenous spread to multiple organs, high HCG levels and a good response to chemotherapy1,12,17,19,22)
. It is preceded by several conditions as follows : 50% arise in molar pregnancies, 25% arise after previous abortions, 23% arise in normal pregnancies and 3% arise subsequent to ectopic pregnancies11)
Choriocarcinoma has a marked tendency to metastasize early by blood-borne dissemination, like in our case. Widespread metastases are characteristic of choriocarcinoam. The favored sites of involvement are the lungs (94% of all metastatic choriocarcinoma), vagina (44%), liver (28%) and brain (28%), followed by the skin, gastrointestinal tract, kidney, breast and bones11,24)
. The clinical signs can be very different, depending on the site of the lesions. The disease often presents with symptoms related to metastatic spread as the primary tumor may remain very small11,22)
Approximately 30% of the patients with choriocarcinoma show metastases at the time of diagnosis20)
. In the case we have described, the patient presented with metastases to the lung, brain parenchyma and lumbar spine. The lung and brain have been described as the most common sites for metastasis in the literature1,2,4,11,12,15,20,21,23,25)
. Yet, metastasis in the musculoskeletal system, such as the spine, is extremely rare and this can be seen from the scant reported cases4,14-16,20,21)
. This current report presents an unusual metastatic choriocarcinoma in the lumbar spine and it extended to the epidural space.
MR image of the lumbar vertebrae in our case revealed a low signal intensity lesion on T1WI and a high signal intensity lesion on T2WI, and this lesion affected the entire L3 vertebral body with the pedicle; the lesion extended to the epidural space with a curtain shape and it was well enhanced. But, on CT and MR image of the lumbar spine, the trabeculation pattern of the L3 vertebra was preserved and the architecture of the cortical bone of the L3 vertebra also is intact. With these findings, our initial impression was an extraosseous extension of vertebral hemangioma that was aggravated during pregnancy and the puerperal period. Pregnancy is a known risk factor for symptomatic conversion of a vertebral hemangioma6,13)
. It is also widely believed that pregnancy and the puerperium are associated with an increased risk of hemorrhage and the aggressive behavior of carvernous malformations20)
Beskonakli et al.4)
reported on a 44-year-old woman with metastatic choriocarcinoma of the thoracic spine that extended to the extradural space and this caused paraplegia. Myelography showed a complete block with intact bony structures at the T5 level. Menegaz et al.15)
reported on a 45-year-old woman with metastatic choriocarcinoma to the lumbar and sacral segments. The radiologic findings showed a predominantly extrathecal intracanalicular process extending from L2 to S1 and compressing the thecalradicular structures. But, the bony structure that was involved was preserved and it exhibited a high signal in T2WI, which suggests microfractures or reactional hyperemia. These findings suggest the choriocarcinoma metastasizing to bony structure has a tendency to invade ahead to the soft tissue and later destroy the bony elements.
Metastases often develop early and they are generally hematogenous because of the affinity of trophoblasts for blood vessels. Because the reported choriocarcinomas were often perfused by fragile vessels, as well as the innate capacity of trophoblastic cells to invade and erode vessel wall, they were frequently hemorrhagic11,24)
. The symptoms of metastases usually result from bleeding at metastic foci. Bony metastases secondary to choriocarcinoma are exceptional. Nonetheless, because the lung and brain are the most common sites of metastasis, many articles1,2,4,11,12,15,20-23,25)
have emphasized that the possibility of choriocarcinoma should be borne in mind when observing parenchymal hemorrhage of the lung or any intracranial bleed in woman of child-bearing age. In our case, the pulmonary and cerebral hemorrhagic content existed and furthermore, a spinal hypervascular mass with feeder vessel was seen on arteriography. As the tumor occupied the L3 vertebral body and this was combined with spinal vasculopathy, which mimicked vertebral hemangioma, we mistook it for a vertebral hemangioma that was aggravated during the puerperal period. Additionally, we missed checking the serum β-HCG level on the patient's laboratory tests. Determining the β-HCG level is necessary for making the diagnosis of choriocarcinoma, and is also useful for the follow-up to detect recurrence and as a prognostic marker1,7,8,11,12,20,22,23,25)
. Choriocarcinoma is characterized by causing autonomous secretion of β-HCG.