Teratoma (non-seminomatous germ cell tumours) - Genitourinary oncology

Teratoma (non-seminomatous germ cell tumours)

Definition

Testicular germ cell tumour which has differentiated along embryonal and extra-embryonal lines.

Incidence/prevalence

32% of testicular tumours; âˆ¼1–2/100,000 per annum.

Age

Any. Peak 20–30 years.

Sex

Males

Aetiology

As for other testicular tumours.

Pathophysiology

Teratomas are more aggressive than seminomas, although this is dependent on the tumour histology. The range of teratoma subtypes reflects the totipotency of the germ cells, which may develop along either embryonic or extra-embryonic cell lines. It has prognostic value.

Clinical features

As for testicular tumours.

Teratoma differentiated (TD): This is a relatively uncommon and usually occurs in infants. The tumour consists of epithelial-lined cysts and stroma contain-ing fully differentiated cells of many types with no features of malignancy. It is associated with a good prognosis.

Malignant teratoma intermediate (MTI): This is a partly solid and partly cystic with some areas appearing more like TD (muscle, stromal cells with epitheliallined spaces) and other areas which show pleomorphism. Fifty per cent of patients have an elevated serum βhCG or Î±FP level.

Malignant teratoma undifferentiated (MTU) or embryonal carcinoma (WHO classification): Typically, these are small, poorly demarcated grey-white lesions which have a variegated appearance due to foci of fleshy and necrotic areas. Microscopically, they appear pleomorphic, with many mitoses and primitive epithelial cells forming irregular sheets, tubules, alveoli and papillary structures. Ninety per cent of patients have elevated serum βhCG or Î±FP levels.

Malignant teratoma trophoblastic (MTT): Tumours containing any area of syncytiotrophoblast and cytotrophoblast arranged in a villous pattern behave aggressively, invading blood vessels. Blood-borne metastases are a common early feature. βhCG and Î±FP are commonly found in the serum and can be detected in cells by immunocytochemistry.

Yolk sac Tumour. Pure yolk sac tumours tend to be found in young children, with yellow-white mucinous lesions. Yolk sac elements are often found with other germ cell tumour elements, when they form solid and papillary lesions which consists of micro-sheets and cords of cells with vacuolated cytoplasm. These are highly malignant and confer a worse prognosis.

Mixed germ-cell tumour: Tumours may consist of any combination of teratoma, seminoma, yolk sac tumour and hCG-containing giant cells (trophoblastic). ‘Tera-tocarcinoma’ in the WHO classification indicates neo-plasms containing both teratoma and embryonal car-cinoma (MTU).

Complications

Spread occurs via the blood stream to lung, liver, brain and bone. Nodal spread also occurs (iliac and paraaortic lymph nodes).

Management

After radical orchidectomy:

Stage I: Retroperitoneal lymph node dissection is often needed if the tumour staging (TNM) showing risk for metastasis. It is often positive, i.e. turning the patient into Stage II.

Stage II and above (metastatic disease): Chemotherapy (triple agent, e.g. cisplatin, etoposide, bleomycin) is used for metastatic disease. If there is residual tumour, with normal markers, surgical resection is indicated to remove tumour bulk, which often is only mature teratoma. If tumour markers do not respond, second choice chemotherapy is tried. Radiotherapy is generally ineffective.

Prognosis

Apart from higher stage disease, the worst prognosis is in those with very high tumour markers and histologically in those which are undifferentiated, vascular invasive or if containing trophoblastic or yolk sac elements. Even for metastatic disease modern treatment has improved the 5-year survival rates significantly to over 90% if all prognostic markers are good, down to 48% for poor prognostic markers. However, when salvage chemotherapy is needed for relapse, response is generally less good although new agents such as paclitaxel and gemcitabine appear to be giving better results.