Definition

• a group of malignant tumours of the testis arising from germ cells.

Epidemiology

 • >90% of all testicular tumours are germ cell tumours.

• Most arise in young men aged from 20 to 45.

Aetiology

• The most consistent risk factor is the presence of cryptorchidism, which increases the risk by 3- to 5- fold.

• Other prenatal risk factors include low birthweight and small- for- gestational age.

• no consistent adulthood risk factors have been identified.

Carcinogenesis

• Most germ cell tumours arise from a precursor lesion known as germ cell neoplasia in situ (GCNIS), characterized by the presence of neoplastic germ cells confined to the seminiferous tubules.

• it is likely that the malignant process begins in foetal life and that GCNIS is present during childhood and young adulthood, during which time further genetic aberrations lead to malignant transformation.

 • One consistently observed structural chromosomal aberration is gain of 12p sequences.

Presentation

 • Most patients present with a painless testicular lump.

• ~10% present with symptoms related to metastatic disease, most commonly back pain from retroperitoneal lymph node metastases or cough/ dyspnoea from pulmonary metastases.

 Serum tumour markers

 • AFP is typically associated with the presence of yolk sac elements.

• β- human chorionic gonadotrophin (HCG) is associated with the presence of syncytiotrophoblastic cells; these may be present individually within a pure seminoma or as an integral component of a choriocarcinoma.

Macroscopy

 • Pure seminomas tend to produce lobulated tan lesions (Fig. 1).

• Teratomas often show cystic and solid areas.

 • Mixed tumours tend to have a variegated appearance.

Histopathology

 • Seminoma is composed of sheets or nests of polygonal cells with clear or eosinophilic cytoplasm and round nuclei containing one or two nucleoli. a lymphocytic infiltrate is commonly present within the tumour.

 • Teratoma is composed of tissues resembling immature fetal- type tissues and/ or mature adult- type tissues.

• Embryonal carcinoma is composed of anaplastic cells with large vesicular nuclei containing large nucleoli. The tumours may grow in solid sheets or form glandular structures.

• Yolk sac tumour is composed of small mildly pleomorphic cells which form a wide variety of architectural patterns, of which the most common are reticular and microcystic.

 • Choriocarcinoma is composed of a mixture of syncytiotrophoblastic and cytotrophoblastic cells. There is often extensive haemorrhage and necrosis.

* Germ cell tumours may be composed entirely of one subtype or a mixture of different subtypes.

Immunohistochemistry

 • Seminoma: Oct3/4+ CD117+ CD30– AE1/ AE3– .

• embryonal carcinoma: Oct3/ 4+ CD117– CD30+ AE1/ AE3+ .

 • yolk sac tumour: Oct3/ 4– Glypican 3+ AFP+ HCG– .

• Choriocarcinoma: Oct3/4– Gypican 3+/– AFP– HCG+ .

Prognosis

 • excellent 5- year survival rates of ~98% in most countries.

• This reflects the high sensitivity of germ cell tumours to modern platinum- based chemotherapeutic regimes.

Fig1. This is a testis from a young man who presented with an enlarging testicular lump. Following an ultrasound scan which was suspicious for a neoplasm, he underwent orchidectomy. The testis has been sliced in the pathology department, revealing this white solid mass in the testis. This appearance is typical of a seminoma, and microscopic examination confirmed this (see Plate 35). Reproduced with permission from Clinical Pathology (Oxford Core Texts), Carton, James, Daly, Richard, and Ramani, Pramila, Oxford University Press (2006), p. 244, Figure 11.14.