Primary mediastinal choriocarcinoma (a case report).
A choriocarcinoma in the mediastinum, without a detectable primary in the gonads or metastasic disease in the retroperitoneal lymph nodes, is termed a primary choriocarcinoma of the mediastinum.
The first authenticated case report, with a review of literature, was made by Fine, followed by similar publications by Benington and Wegner. A search of the literature brought to light only one case from India by Prusty, diagnosed on clinical features, radiology and biopsy from the mediastinal mass. A meticulous autopsy study was possible in the present case, by which we were able to confirm the diagnosis.
A 25-year-old male painter came to hospital with a swelling in the left side of the neck, dry cough, low grade fever for one month. and haemoptysis for 10 days. There was also a history of weakness of the left arm for a week and of the right arm and leg for a few hours. The swelling in the neck was gradually increasing in size. He had lost weight during the last month. He smoked heavily, but there was no history of contact with tuberculosis.
He was emaciated with a normal pulse and normal blood pressure in both the arms. He was mildly fibrile and had a dry, brassy cough. The swelling in the left supraclavicular region measured 7.5 x 7.5 x 3.5 cm. with dilated veins over it. The trachea was shifted to the right. Air entry was diminished and there was dullness in the left upper zone, with crepitations all over the lungs.
The fundi were normal. There was right upper motor neurone VII nerve palsy, left Horner's syndrome, and flaccid hemiparesis of the left leg. The patient died within 14 hours of admission.
The clinical impression was Pancoast's tumour with metastasis in the 1ung and embolus in the left middle cerebral artery territory.
Then; was bilateral gynecomastia and there were two masses in the left superior mediastinum. The larger mass (7 x 4.5 x 3.5 cm), was partly encapsulated and infiltrating into the surrounding soft tissue including the neck veins and nerves. The smaller mass (2.5 x 1.5 x 1 cm) was well encapsulated and free from the arch vessels. Both the masses were soft to firm and greyish white, with extensive areas of haemorrhage and necrosis.
Both the lungs showed multiple haemorrhagic nodules, varying in diameter from 5 mm to 3 era. A similar haemorrhagic nodule, 1.5 cm, in diameter was found in the right kidney. The retroperitoneal lymph nodes were not enlarged. The testes were unremarkable. There was no scar, cyst or mass, and normal stringing of the seminiferous tubules was possible. The brain appeared normal,
Histologically, the two mediastinal masses were identical in appearance: bizarre syncitiotrophoblastic and cyto-trophoblastic cells arranged in sheets and clusters without any villous structures with the appearance of a choriocarcinoma. There were extensive aseas of haemorrhage and necrosis. The nodules in the lungs and kidney consisted of metastatic deposits.
Multiple sections of the testes showed seminiferous tubules (ST) with normal spermatogenesis, separated by oedematus stroma containing sparse Leydig cells (LC); the ratio LC/ ST was 4:1 (normal-2.8:1). The thyroid showed follicles of varying size separated by thin fibrous tissue infiltrated by lymphocytes. Most follicles were lined by tall columnar epithelium and contained colloid with scalloping on the margins-a picture suggestive of thyrotoxicosis.
Primary choriocarcinoma of the mediastinum occurs in both sexes, but is extremely rare. It is commoner in man and is most often seen in the second and third decades of life.
The histogenesis remains obscure, although an origin from misplaced germ cells is strongly supported by the anatomic demonstration of widespread pathways of migration of germ cells during embryogenesis to locations like the retroperitoneum, mediastinum and neck.
The possibility of metastasis from an occult testicular primary must be ruled out before making a diagnosis,, be cause of the tendency for testicular tumours to be quite small and even burnt out at the time of metastasis. Germ cell tumours of testicular origin rarely metastasise exclusively to the mediastinum. They spread first to the retroperitoneal lymph nodes, often bypassing the mediastinum, via the thoracic duct. The present tumour arose in the mediastinum (1) in the absence of a detectable testicular primary, and (2) in the absence of metastatic disease in the retroperitoneal lymph nodes.
The trophoblastic cells of the tumour tissue elaborate massive amounts of human chorionic gonadotrophins (HCG) which give a positive pregnancy test.,, HCG also causes Leydig cell hyperplasia leading to increased formation of testosterone and its estrogen-like metabolites. The estrogenic hormones could account for the adverse effect on testicular germinal epithelium resulting in the infertility and bilateral gynaecomastia so often observed in these patients., The a-chain of HCG, which shares with TSH an almost identical polypeptide sequence, causes hyperplasia of the thyroid follicles resulting in a clinical and histological picture akin to thyrotoxicosis. The development of biochemical and clinical thyrotoxicosis depends upon the duration of the choriocarcinoma and the levels of HCG.
A noteworthy feature of mediastinal choriocarcinoma is that it has a distinctly poorer prognosis than its testicular counterpart., This is probably due to the fact that mediastinal tumours are not subject to the restrictive influence of the tunica albugenea as in the testis, hence they attain a large size and often invade the adjacent vital structures by the time diagnosis is made. Triple drug chemotherapy gives an average survival of 3-4 months, the longest survival on record being 17 months.