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2007-10-01-15 Non-gestational mediastinal choriocarcinoma mimicking an early pregnancy © Manson www.thefetus.net/
Non-gestational mediastinal choriocarcinoma mimicking an early pregnancy

Francois Manson, MD.

Fécamp, France

 

 

Case report

We report an unusual case of a 22-year-old woman (G0P0) presented with the 10-week’s amenorrhea, after her birth control pills’ withdrawal. At first, her positive high serum hCG level (5000 IU/l) lead to the diagnosis of pregnancy. She didn’t have any other problems. Her uterine size was normal and a transvaginal ultrasound found a normal uterus and ovaries with no signs of an extrauterine pregnancy.

Image 1: Ten weeks amenorrhea - vaginal scan. The image shows an "empty" uterus without any evidence of hemoperitoneum.

 

Images 2, 3: Ten weeks amenorrhea - vaginal scan. A normal appearance of the ovaries.

 

The increased levels of the HCG, despite of normal sonographic and clinical examinations were suspected from an atypical extrauterine pregnancy and the laparoscopy and hysteroscopy were performed.

  • The laparoscopy was normal;

  • The hysteroscopy showed a normal uterine cavity with a thin endometrium.

Histological study of the endometrium found a normal endometrium without any evidence of chorionic villi.

During the postoperative period, the hCG levels remained increased. Considering the previous findings we supposed an extrapelvic source of hCG production and a whole body’s computer tomography was performed. The scan of the thorax revealed a 6 cm, heterogenous, well-demarcated mass of the anterior upper mediastinum. Its biopsies obtained by mediastinoscopy showed mostly necrotic, hemorrhagic tumor with malignant proliferation of cytotrophoblastic and syncytiotrophoblactic cells leading to the diagnosis of the isolated mediastinal choriocarcinoma. This diagnosis was confirmed by immunohistochemistry, which demonstrated positive staining for HCG of tumor cells.

The genotype of the tumor was compared with supposed parental genotypes (the patient one and her husband one), to assess the gestational or non-gestational origin of the lesion. The genotype of the tumor was strictly identical with the patient’s genotype without any paternal features. These results led to the diagnosis of the non-gestational choriocarcinoma.

Before initiation of treatment, the patient had been checked for other anomalies and an elevated prolactin level was found (112.4 ng/ml; the normal range is between 4.6 and 15.8 ng/ml). The patient underwent polychemotherapy, and after four courses the hCG level returned to a normal level with complete regression of the tumor. The patient is five years after therapy with no signs of recurrence and is considered to be cured of the disease.

Discussion

Non-gestational choriocarcinoma represents a specific type of germ-cell tumors. By definition, germ-cell tumors are derived from germ cells. Their histological structure reflects different stages of embryonal development, and may include choriocarcinomas, seminomas, embryonic carcinomas, mesoblastomas, yolk sac tumors and teratomas. By nature, the germ cell tumors are mostly located in gonads, however, exceptionally they can be found in other locations. If isolated, without any gonadal lesion, these ectopic germ cell tumors are called “isolated extragonadal germ cell tumors”.

Choriocarcinomas derive from the cytotrophoblastic and syncytiotrophoblastic cells. The mediastinum is the main, but non exclusive ectopic site of these tumors. Other locations include retroperitoneum, sacrococcygeal area, pineal area and supra-hypophyseal area.

These tumors are very rare and arise essentially in young men (95% of the cases). Choriocarcinoma represents 0.1 to 0.5% of all tumors of the mediastinum. These neoplasias are often discovered randomly or due to symptoms attracting attention as thoracic pain, dyspnea, and cough. We have found only two cases with initial gynecological presentation in the literature.

On CT scan, mediastinal choriocarcinomas are masses in the anterior and upper mediastinum, located in front of the great vessels. They are heterogenous with frequent hemorrhagic and necrotic areas.

Tumor markers (b-hCG in case of choriocarcinoma) are helpful in diagnosis, evaluation of the treatment and early detection of recurrences.

Precise diagnosis is based on the pathological study of tumor fragments obtained surgically. In certain cases, immunohistochemistry can be helpful.

Choriocarcinomas are frequently associated with a paraneoplastic syndrome:

  • Hyperthyroidism is present in 25 to 60% of the cases and can be biochemical or clinical. It is caused by the structural similarity between the hCG and TSH which is responsible for a TSH activity of the hCG;

  • Hyperprolactinemia was reported in several cases of choriocarcinoma. Its pathophysiology remains unknown, but it could be related to a prolactin-like protein production by syncytiotrophoblastic cells. This phenomenon could explain the amenorrhea as it was presented in our case.

Chemotherapy, including platinum-based chemotherapy, remains the first choice of treatment. Surgery can be recommended to remove residual lesions. The prognosis of extra-gonadal choriocarcinoma seems to be worse than the ones in the gonadal location or gestational choriocarcinoma. The worse prognosis seems to be related to the larger size of the tumor at the time of diagnosis.

There are two theories trying to explain the pathophysiology of the extragonadal choriocarcinomas and germ cell tumors:

  • The gonoblastic theory - this theory suppose an aberrant migration of the gonoblasts during embryonic life. Normally, the gonoblasts initially appear outside the embryo, in the wall of the yolk sac, and later migrate through the vitellin canal to the urogenital crests. An abnormal migration of these cells is supposed to be responsible for the abnormal locations of the germ cell tumors (e.g. epiphysis, mediastinum, sacrococcygeal region). These cells have higher malignant potential and could survive in their ectopic location and transform in germ cell tumors.

  • Metastatic theory was proposed by Prym in 1927, and explains the presence of the extragonadal germ cells tumors by metastatic process of the primary gonadal occult or regressed tumors. This theory was supported by the fact that in certain cases of extragonadal germ cell tumors, there were also a gonadal lesions present (microinvasive carcinomas, in situ germ cell tumors, atypical germ cells).

Conclusions

Extragonadal non-gestational choriocarcinomas are very rare. Their manifestation as an early pregnancy appears exceptional. However, this entity should be taken into consideration in the cases of unclear early pregnancy, especially if the following sonographic findings accompany the higher levels of the hCG:

  • the abnormal thickness of the endometrium without vaginal bleeding;

  • the absence of the corpus luteum;

  • the absence of the sings of the pelvic ectopic pregnancy.

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