MALIGNANT GERMINAL NEOPLASMS OF THE MEDIASTINUM

Primary mediastinal germ cell tumors

Mediastinal germ cell tumors share similar histopathological, immunohistochemical, and molecular features with their counterparts in the gonads. Therefore, proper clinical and radiological evaluation of patients with an anterior mediastinal mass becomes essential in the final interpretation of these tumors. The gold standard for the diagnosis of these tumors remains histopathological evaluation. However, immunohistochemical stains and molecular studies also provide an aid in cases in which the histology is not typical. It is also important to keep in mind that a small mediastinoscopic biopsy may not be representative of the entire neoplasm. In this review, we will provide our perspective regarding histopathological diagnosis, staging, immunohistochemical and molecular profile, and briefly family of tumors address pertinent epidemiological, clinical and treatment options. However, the main emphasis is to review the process of pathological assessment in pre and post-treated tumors. Knowledge of the different growth patterns and histological associations is important, mainly when confronted with mediastinoscopic biopsies, which ultimately will determine treatment options.

[Mediastinal Tumors]

If mediastinal tumours cause symptoms these are related to their anatomical localization or a paraneoplastic syndrome. The differential diagnosis is based on the clinical situation with finding the lesion, and, furthermore, taking into account the age and sex of the patient, and the mediastinal compartment where the lesion is located. Cross-sectional radiographic diagnostic is essential for defining the therapeutic strategy. The anterior mediastinum is dominated by thymic tumours, mediastinal lymphomas, germ cell tumours and ectopic mediastinal poiters. The middle mediastinal compartment is the most frequent place of mediastinal cystic tumours, whereas the posterior mediastinum is the domain of neurogenic tumours. For selected cases a tissue biopsy is required. Surgery is the mainstay for most mediastinal tumours. Median sternotomy is the most frequent conventional surgical technique while minimally invasive surgery with thoracoscopic and above all robot assisted operation techniques are increasingly frequent. Combined chemotherapy and modern radiotherapy are essential components of the comprehensive treatment for mediastinal tumours.

Apoptosis and proliferative activity in mature and immature teratomas of the mediastinum

BACKGROUND

Mediastinal teratomas are the most frequent mediastinal germ cell tumor. Whereas mature teratomas are benign tumors, immature teratomas are malignant. The purpose of this study was to find characteristics that could be used to distinguish between the growth and prognosis of the two teratoma types.

METHODS

Twenty-four mediastinal teratomas (18 mature and 6 immature) were examined for apoptosis by 3'-end labeling of DNA and stained immunohistochemically for proliferating cell nuclear antigen, Bcl-2, Bax, p53 protein, and alpha-fetoprotein (AFP) expression in formalin fixed, paraffin embedded specimens.

RESULTS

AFP was expressed in both immature teratomas and mature teratomas. Whereas p53 protein was expressed by most teratomas, p53 gene mutation was observed in only one patient with an immature teratoma in which the same mutation occurred in all tumor tissue components tested. Bax protein expression was relatively diffuse in mature teratomas but was focally expressed in immature teratomas. Bcl-2 protein was expressed focally in both mature and immature teratomas. Although the proliferative index was significantly higher in immature teratomas compared with mature teratomas (P < 0.001), the apoptotic index (AI) was significantly higher in mature teratomas compared with immature teratomas (P < 0.05). All patients except one in this study remain alive and disease free after undergoing tumor resection.

CONCLUSIONS

The relatively high AI in mature teratomas may be due to the overexpression of the p53 protein. In contrast, immature teratomas exhibited higher proliferative activity and lower rates of apoptosis, which may explain the more aggressive behavior of these tumors. However, patients with immature mediastinal teratomas have a good prognosis if the tumor is resected completely after chemotherapy.

Primary malignant mediastinal germ cell tumours: improved prognosis with platinum-based chemotherapy and surgery

A retrospective analysis was performed of 18 patients with primary malignant germ cell tumours of the mediastinum treated with platinum-based chemotherapy between 1977 and 1990. All seven patients with pure seminoma were treated initially with chemotherapy and four of these patients received additional mediastinal radiotherapy. Only one patient relapsed; his initial therapy had included radiotherapy and single-agent carboplatin and he was successfully salvaged with combination chemotherapy. With a follow-up of 11 to 117 months (median 41 months) all seven patients with seminoma remain alive and disease free giving an overall survival of 100%. Eleven patients had malignant non seminoma; following chemotherapy eight of these had elective surgical resection of residual mediastinal masses. Complete remission was achieved in nine (82%) patients, however, one of these patients died from bleomycin pneumonitis. With a follow-up of 12 to 113 months (median 55 months) eight of 11 (73%) patients with malignant mediastinal teratoma remain alive and disease free.

The role of radiotherapy in the treatment of primary mediastinal seminoma

Nine patients with primary mediastinal seminoma were treated with radiotherapy. All patients achieved complete response on chest radiography. None of the three patients treated with whole mediastinal irradiation relapsed. Four of the six patients with involved-field irradiation had marginal relapses, suggesting the efficacy of the whole mediastinal irradiation.

Genetic abnormalities in men with germ cell tumors

We retrospectively reviewed the genetic abnormalities detected clinically in 455 men with advanced germ cell tumors referred for chemotherapy. Of the patients 49 had extragonadal and 406 had testicular germ cell tumors. Of 19 patients with mediastinal germ cell tumors 4 (21 per cent, 3 with teratocarcinoma and 1 with endodermal sinus tumor) had Klinefelter's syndrome. Three of these patients had a 47XXY and 1 had a 48XXYY karyotype. No Klinefelter's syndrome was observed among 30 consecutive patients with retroperitoneal germ cell tumors or among the 406 with testicular tumors. Karyotypes of 35 consecutive patients with testis cancer without evident congenital abnormalities showed normal chromosomal patterns. We found 2 patients with Down's syndrome and testicular tumor, for an incidence of 0.5 per cent (probably significant). We also describe 2 cases of nonseminomatous testicular cancer and Marfan's syndrome (0.5 per cent incidence versus a 5 of 100,000 incidence of Marfan's syndrome in the general population). Apparently, genetic abnormalities are increased in men with germ cell tumors and we discuss the significance of this association.

A multidisciplinary approach to primary nonseminomatous germ cell tumors of the mediastinum

The introduction of cis-platinum-based chemotherapy has dramatically improved the prognosis for patients with primary nonseminomatous germ cell tumors of the mediastinum. Since 1978, 12 male patients (mean age, 29 years) have been seen with a large mediastinal mass, normal testes, and abnormal testicular tumor markers. Eleven patients had raised alpha-fetoprotein levels (median, 1,300 micrograms/L; normal, less than 10 micrograms/L), and 3 had elevated levels of the beta fraction of human chorionic gonadotropin (median, 8,000 IU/L; normal, less than 5 IU/L). Two patients were treated by primary surgical intervention followed by chemotherapy. Ten patients were treated with primary chemotherapy (cis-platinum, vinblastine sulfate or etoposide, and bleomycin sulfate), and this was followed by timed surgical excision of the tumor mass in 7. Six (60%) patients responded to primary chemotherapy with normalization of tumor markers. In this group there was 1 postoperative death and 1 recurrence. The 4 remaining patients are alive and free from disease at a mean of five years. Of the 4 patients with persistently elevated tumor markers, 2 died within six months, 1 is alive with recurrence, and 1 is lost to follow-up at three months. Patients whose tumor markers return to normal after cis-platinum-based chemotherapy have a good long-term prognosis following radical surgery. If the tumor markers remain elevated, the prognosis is poor.

Endodermal sinus tumor of the mediastinum. A report of seven cases and review of the literature

Primary mediastinal endodermal sinus tumor is rare, and to date only 49 cases have been described in the English-language literature. Seven new cases are reported. Light microscopic examination showed characteristic features including papillary, reticular, tubular and solid growth patterns, complete or incomplete Schiller-Duval bodies and intracellular or extracellular periodic acid-Schiff-positive material. Immunohistochemical studies showed alpha-1-antitrypsin in seven, alpha-fetoprotein in seven, keratin in six, and carcinoembryonic antigen in four cases. The beta subunit of human chorionic gonadotropin, albumin, fibronectin, and transferrin were not found in any case. Electron microscopic studies performed in four cases showed intracellular and extracellular basement membrane-like material, multiple large multivesicular bodies, desmosomes and microvilli. Mediastinal endodermal sinus tumor can and must be differentiated from poorly differentiated adenocarcinoma metastatic or extending to the mediastinum because of the distinctly different prognoses and therapies. In spite of modern chemotherapy, the prognosis of mediastinal endodermal sinus tumor remains poor. The single most important prognostic indicator is whether the tumor mass can be completely excised before or after chemotherapy.

Malignant germ cell tumor of the anterior mediastinum with leukemia-like infiltration

We present here a rare autopsy case of malignant germ cell tumor with leukemia-like infiltration of the anterior mediastinum in a 35-year-old male. Chest X-rays revealed an abnormal mediastinum, which was diagnosed as thymoma. During the course of treatment, huge abnormal cells 40-50 mu in size were found in the peripheral blood smear and disseminated bone metastasis of the malignant thymoma was suspected. The tumor was resistant to both chemotherapy and radiotherapy. The patient died of respiratory failure. The autopsy disclosed a huge tumor measuring 24 X 13 X 10 cm in the anterior mediastinum. Histological findings of the tumor revealed cells which had spread to almost all organs, indicating leukemia-like infiltration. This pattern of metastasis has been reported in the cancer of non-hematologic origin under the term "carcinocythemia (CCA)". To our knowledge, the present case is the first report of a leukemia-like infiltration in case of malignant germ cell tumor. Careful serial section revealed no primary foci in either testis.

Anterior mediastinal endodermal sinus (yolk sac) tumor in a female infant

The first known case of primary anterior mediastinal endodermal sinus (yolk sac) tumor in a female patient, occurring in a 20-month-old infant, is reported. The child presented with cough, fever, and listlessness. Chest x-ray revealed a right anterior mediastinal mass. At thoracotomy a large anterior mediastinal tumor extending from the neck to the diaphragm was found, and was almost totally resected. Microscopically, the tumor displayed many of the histologic patterns observed in EST. Other neoplastic germ cell elements were not identified. The ultrastructural and immunohistochemical findings further confirmed the diagnosis. Serum alpha-fetoprotein (AFP) level, determined during surgery, was elevated to 65,200 ng/ml, whereas serum beta-human chorionic gonadotropin level was normal. Postoperatively, combination chemotherapy consisting of vinblastine, bleomycin, cisplatin, dactinomycin, cyclophosphamide, and doxorubicin was administered with a maintenance program. After 18 weeks on this regimen all the findings were normal, including serum AFP level. The child is well and disease-free 25 months after diagnosis.

Intracranial germ-cell tumors: natural history and pathogenesis

The natural history of primary intracranial germ-cell tumors (GCT's) is defined from 389 previously published cases, of which 65% were germinomas, 18% teratomas, 5% embryonal carcinomas, 7% endodermal sinus tumors, and 5% choriocarcinomas. Intracranial GCT's display specificity in site of origin. Ninety-five percent arise along the midline from the suprasellar cistern (37%) to the pineal gland (48%), and an additional 6% involve both sites. The majority of germinomas (57%) arise in the suprasellar cistern, while most nongerminomatous GCT's (68%) preferentially involve the pineal gland (p less than 0.0001). The age distribution of afflicted patients is unimodal, centering with an abrupt surge in frequency in the early pubertal years; 68% of patients are diagnosed between 10 and 21 years of age. Nongerminomatous GCT's demonstrate an earlier age of onset than do germinomas (p less than 0.0001). Prolonged symptomatic intervals prior to diagnosis are common in germinomas (p = 0.0007), in suprasellar GCT's (p = 0.001), and among females (p = 0.02). Parasellar germinomas commonly present with diabetes insipidus, visual field defects, and hypothalamic-pituitary failure. Nongerminomatous GCT's present as posterior third ventricular masses with hydrocephalus and midbrain compression. Germ-cell tumors may infiltrate the hypothalamus (11%), or disseminate to involve the third ventricle (22%) and spinal cord (10%). Among a subpopulation of 263 conventionally treated patients, two factors were of prognostic significance: 1) histological diagnosis; germinomas were associated with significantly longer survival than nongerminomatous GCT's (p less than 0.0001); and 2) staging of the extent of disease; this emphasizes the ominous character of involvement of the hypothalamus (p = 0.0002), third ventricle (p = 0.02), or spinal cord (p = 0.01). Specific recommendations regarding the necessity of histological diagnosis and staging of the extent of disease are made in light of modern chemotherapeutic advances. The pathogenesis of GCT's may be revealed by their specificity of origin within the positive (suprasellar cistern-suprachiasmatic nucleus) and negative (pineal) regulatory centers for gonadotropin secretion within the diencephalon. The abrupt rise in age distribution at 10 to 12 years suggests that the neuroendocrine events of puberty are an "activating" influence in the malignant expression of these embryonal tumors.

The development of non-germ cell malignancies within germ cell tumors. A clinicopathologic study of 11 cases

Eleven male patients had germ cell tumors of the testis (7), mediastinum (3), or retroperitoneum (1) in which non-germ cell malignancies developed. Such malignant non-germ cell elements were present in the primary excisions of five patients and were subsequently found in additional resected tissue in 10 of 11 patients. In the patients who had multiple pathology specimens examined, a progression from atypia to predominant non-germ cell malignancy was often found. The authors believe these malignant elements arose within teratomatous foci, since eight of nine cases had teratoma in the primary tumor, and teratoma was found in subsequently resected tissue in one additional case. Cisplatin therapy frequently "unmasked" the non-germ cell malignant elements by destroying the more chemosensitive germ cell cancers. The prognosis was worst for five patients who developed progressive embryonal rhabdomyosarcoma: two of these patients died of local spread of tumor, whereas a third died of metastatic sarcoma. Only one patient, who had total surgical excision of rhabdomyosarcoma, survived. Other forms of sarcoma that developed within germ cell tumors did not appear to adversely affect the prognosis beyond that of teratoma. It is currently recommended, when feasible, that patients with teratoma and sarcoma undergo total surgical excision. Further treatment with cisplatin regimens, after eradication of the germ cell component, has not been helpful. The role of other forms of chemotherapy remains speculative.

Benign clinical behavior of immature mediastinal teratoma in infancy and childhood: report of two cases and review of the literature

Germ cell tumors of the mediastinum can be divided into three categories: 1) mature teratomas which have all elements at a mature level; 2) immature teratomas which are similar to the mature teratomas, but also contain immature epithelial or mesenchymal elements or blastema; and 3) embryonal tumors which contains elements which are recognized as dysgerminoma, embryonal carcinoma with or without yolk sac elements, and choriocarcinoma. Immature teratomas are the rarest type, accounting for only about 1% of mediastinal teratomas. Two cases of immature teratoma of the mediastinum occurring in infants are reported. One tumor was completely excised. The child is well without evidence of disease two years later. The other immature teratoma was unresectable. Biopsy showed it to be similar to the teratoma that was excised. No postoperative treatment was given. The tumor has not changed appreciably in size, but the child has grown normally for six years so that the tumor mass, which initially filled his chest, is now evidenced as mediastinal widening. A review of the reported cases of immature teratomas in the mediastinum shows that the prognostic value of the histologic appearance of these tumors has not been developed to the same degree as it has for teratomas in the ovary or the sacrococcygeal region. The immature teratomas that occur in infants behave as mass lesions as do the mature teratomas. Immature teratomas in the mediastinum of children in their late teens and in young adults behave as highly malignant tumors similar to the embryonal carcinomas.

Coarctation of the aorta from a mediastinal germ cell tumor: a case report

A 20-yr-old male had compression of the thoracic aorta by a large malignant mediastinal germinoma. The symptoms and signs that simulated coarctation of the aorta included hypertension, markedly decreased femoral pulses, and a systolic murmur that radiated to the back. Following X-ray therapy, the femoral pulses were palpable and the blood pressure became normal. To our knowledge, compression of the aorta by a malignant teratocarcinoma with manifestations mimicking coarctation of the aorta has not been reported.

Vinblastine (VLB), bleomycin (BLEO), cis-diamminedichloroplatinum (DDP) in disseminated extragonadal germ cell tumors. A Southwest Oncology Group Study

Nineteen patients considered to have metastatic primary extragonadal germ cell cancer were entered on a Phase II chemotherapy study using as induction therapy a combination of vinblastine (VLB) 12 mg/m2 day 1, bleomycin (BLEO) 15 U/m2 I.V. or I.M. twice weekly, and cis-diamminedichloroplatinum (DDP) 15 mg/m2 days 1-5, with vinblastine and DDP repeated at 28-day intervals for four months. All complete or partial responders were then placed on a maintenance regimen of vinblastine 12 mg/m2 alternating monthly with actinomycin-D 1.5 mg/m2 day 29, and chlorambucil, 10 mg/m2 P.O. days 32-37. There were three complete remissions (CR's), six partial remissions (PR's), and two stable disease. The response rate (CR's mpr's) was 56%; however the mean duration of response was only two months (range, 1-8 months). Drug toxicity was significant and there was one toxic death. Unlike patients with disseminated testicular cancer, patients with primary metastatic extragonadal germ cell carcinoma appear to do less well on this particular drug regimen. Further investigation using different drug regimens seems necessary.

An established human cell line derived from a malignant mediastinal teratoma

An established cell line derived from a human malignant mediastinal teratoma is described. The cell line was composed of slightly atypical fibroblast cells with a population-doubling time of 24 h at the exponential growth phase. The reason why the emerging cell line became fibroblastic although other tissues were present in the original tumor may be that fibroblasts so readily grow in culture. Chromosome banding showed a hypertriploid stemline number, S = 78. Almost all of the analysed karyotypes had seven markers in common. Eleven other markers, occurring at low frequency, were also detected. The origin of all markers except one could be deduced.

The management of extratesticular seminoma without gonadal involvement

Diagnosis, treatment and follow-up of 8 patients from 1955 to 1975 with extratesticular seminoma are presented. In 5 patients, the neoplasm developed in the mediastinum and in 3 in the retroperitoneum. All the patients were treated by radiation therapy after resection or biopsy. In the entire group, no tumor was diagnosed in the testes. Two patients expired with disease, one after 2 months due to pneumonia, and the other 5 years after diagnosis (10 months after treatment) due to cerebral metastases. Two patients died 12 and 16 years after diagnosis and treatment. At death, they were free of seminoma and the cause of death was a second malignancy. Four patients are alive and healthy, free of disease, 5, 10, 13, and 17 years after diagnosis and treatment. In essence, of the 8 patients, only one actually died of disease, and he was not adequately treated. We feel that this is an entity with an excellent prognosis if adequately and appropriately treated with radiation. We recommend not to perform an orchiectomy when the testes are clinically normal, and to follow the patient closely after treatment.

[A comparative clinical and pathological study on the classification and prognostic features of 57 thymomas. I. Microscopy and ultrastructural pathology (author's transl)]

Fifty-seven thymomas, defined as neoplasms of the epithelial-reticular framework cells of the thymus, were assessed in respect to histologic type, inclusive of there ultrastructural aspects. The median age of the 57 patients was 40.4 years, with a range of 2 1/2--72 years. All neoplasms were located in the anterior mediastinum. The tumours in 40 cases were encapsulated and without invasion of adjacent tissue or implants (equal to non-invasive thymomas). The tumors in 17 cases were invasive of adjacent tissue, particularly mediastinal pleura, pericard and trachea. Six of 57 patients (equal to 10.5%) with thymomas have had a thoracic and supraclavicular lymph node metastasis, and osteolytic metastases in the vertebrae and sternum. Thirty-seven (equal to 64.9%) were so-called lympho-epithelial, 7 (equal to 12.3%) pure epithelial, 4 (equal to 7.0%) atypical (or anaplastic) with granulomatous focuses, 3 (equal to 5.3%) carcinoid and one (equal to 1.8%) seminomatous tumors. One patient have had a thymic cyst as a tumor-like conditions of the thymus, and four patients (equal to 7.0%) have had a thymo-lipoma. The histologic type of thymoma had no proof value in predicting prognosis with the exception of the so-called atypical or anaplastic thymoma. The fine structural aspects of thymomas and the fine structural differential diagnosis of anterior mediastinal tumors are discussed.

Mediastinal teratoma masquerading as idiopathic enlargement of the right atrium

A chest roentgenogram of an asymptomatic 22-year-old man revealed prominence of the right heart border characteristic of idiopathic dilatation of the right atrium. On further evaluation, a malignant teratoma was found. The importance of including teratoma and idiopathic enlargement of the right atrium in the differential diagnosis of abnormalities of the right heart border is discussed.

Humoral antibodies against spermatopoietic cells associated with mediastinal germinoma

A case of mediastinal germinoma in a 21-yr-old male is reported. The neoplasm exhibited a morphology similar to that of a testicular seminoma and was heavily infiltrated by lymphocytes and plasma cells. Germinal centres were also present in lymph follicles. Humoral antibodies (IgG), specific for spermatopoietic tissue, were present in the patient's serum. Antibody titres declined after surgical removal of the germinoma over a period of 2 yr, and antibody is no longer detectable at the present time. The implications of this observation are discussed with regard to defence mechanisms of the tumour host, and to the histogenesis of these rare neoplasms.

Testicular tumours

With modern methods of diagnosis, staging and treatment, seminoma is a highly curable tumour. The worse results for the treatment of teratomas are likely to improve particularly as methods for detection of the tumour improve and as types of treatment are increasingly combined in a way which takes account of the biology of the tumour and the strength and limitation of each treatment modality. Stage I and II teratoma should receive irradiation after orchidectomy although when bulky retroperitoneal disease is present irradiation alone is rarely capable of securing local tumour control. In these cases chemotherapy may achieve nodal regression preparatory to irradiation. Excision of residual masses after irradiation should be considered in teratoma. Chemotherapy is the treatment of choice for disseminated teratoma but maintaining tumour control poses problems. Whole lung irradiation following chemotherapy is being assessed in selected patients.