Seminoma - Genitourinary oncology

Seminoma

Definition

These are testicular tumours of germ-cell origin which have differentiated along the spermatocytic line.

Incidence/prevalence

Most common testicular tumour (40%); âˆ¼2/100,000 p.a.

Age

Peak age 35–50 years.

Sex

Male

Aetiology

As for testicular tumours. Seminoma is the most common type to occur in maldescended testes.

Clinical features

As for testicular tumours. Bilateral involvement is rare.

Macroscopy/microscopy

The tumour appears as a homogeneous firm white mass, amidst normal, brown testis. Usually there is no evidence of haemorrhage or necrosis. There are three histological subtypes of seminoma, termed classic, anaplastic and spermatocytic (British Testicular Tumour Panel) depending on the microscopic features:

·        Classic seminoma (85% of seminomas). Sheets of large, polygonal cells with clear cytoplasm (vacuolated and glycogen containing) and small central dark-staining nuclei. The presence of fibrous septa containing prominent lymphocytic infiltration is a favourable prognostic factor.

·        Anaplastic seminoma (5–10% of seminomas). This type is more aggressive than classical seminoma. It shows marked pleomorphism and increased mitotic activity.

·        Spermatocytic seminoma (4–6% of seminomas). This is a rare neoplasm which occurs in slightly older patients. It is not associated with intratubular germ cell neoplasia. The cells are pleomorphic, have a high mitotic rate and contain abundant eosinophilic cytoplasm. They do not contain glycogen. Amongst the larger cells, are small cells which resemble spermatocytes. Despite the apparent histological features of aggressiveness they have an indolent growth and show virtually no tendency to metastasise.

Around 10% of seminomas contain trophoblastic giant cells, and these produce human chorionic gonadotrophin, which may be detectable in the blood. However, this does not appear to affect prognosis, or response to treatment.

Complications

i.      Seminomas tend to spread via the lymphatics initially, to the iliac and paraaortic lymph nodes.

ii.      Bloodstream spread is a late feature.

Management

All patients undergo radical orchidectomy as an initial measure.

Stage I: Localised radiotherapy or 1–2 cycles of carboplatin chemotherapy reduce relapse to around 1–3%.

Stage II and above (metastatic disease): Generally advised to have combination chemotherapy, usually with cisplatin/etoposide/bleomycin. Residual tumour is treated with further chemotherapy or radiotherapy.

All patients should be regularly followed up with tumour markers and imaging, e.g. chest X-ray +/− ab-dominal USS or CT as indicated.

Prognosis

More than 99% of cases stage I disease have a normal lifespan. Even with metastatic disease 90% of these fall into the good prognosis category and they have an 86% 5-year survival. There is a higher risk of contralateral cancer, but this usually responds well to treatment.