Epidemiology
Germ cell tumours (GCT) are rare, but account for 95% of testicular tumours and 3–5% of ovarian malignancies. They are the commonest cancer in men aged 20–40 years and the peak incidence of ovarian GCT is in young women and adolescent girls. They represent one of the few groups of solid tumours for which the majority of patients can expect to be cured.
Extra-gonadal tumours account for less than 10% of all germ cell tumours. They occur in midline structures, most commonly in the mediastinum (50–70%) and retroperitoneum (30–40%), and rarely the brain, head and neck. In the mediastinum the peak incidence is in the third decade of life.
Aetiology
A family history of testicular cancer is one of the strongest risk factors for disease, although a definite genetic link has not yet been identified. More than 80% of testicular cancers express 12p gain, often as an isochromosome of 12p (i12p), where one arm of the chromosome is lost and replaced with an exact replica of the other arm.
Carcinoma in situ (intratubular neoplasia) is the precursor of testicular germ cell cancer and is found in addition to the invasive component.
Pathophysiology
Seminoma and dysgerminoma
Seminoma accounts for 50% of malignant germ cell tumours in men, with a peak incidence between the ages of 30 and 40. Spermatic seminoma is more common in older men, between the ages of 60 and 70. Ovarian dysgerminoma is directly comparable with testicular seminoma and accounts for the majority of cases of ovarian GCT.
The majority of patients (75%) present with disease confined to the testis or ovary. Spread is usually predictable from para-aortic to supradiaphragmatic nodes, and then to extranodal sites. Growth is slow, and microscopic disease may take up to 10 years to present clinically. Seminomas and dysgerminomas do not produce a reliable tumour marker with which to monitor disease, but hCG can be elevated in 10–25% of cases.
Non-seminoma
Disease spread occurs earlier than in seminomas, and therefore only 50% of patients present with localised disease. AFP and hCG tumour markers are elevated in approximately 75% of cases.
Clinical presentation
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