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Primary germ cell tumors (GCTs) of the testis, arising by the malignant transformation of primordial germ cells, constitute 95% of all testicular neoplasms. Infrequently, GCTs arise from an extragonadal site, including the mediastinum, retroperitoneum, and, very rarely, the pineal gland. This disease is notable for the young age of the afflicted patients, the totipotent capacity for differentiation of the tumor cells, and its curability; about 95% of newly diagnosed patients are cured. | Chapter 092. Testicular Cancer Primary germ cell tumors GCTs of the testis arising by the malignant transformation of primordial germ cells constitute 95 of all testicular neoplasms. Infrequently GCTs arise from an extragonadal site including the mediastinum retroperitoneum and very rarely the pineal gland. This disease is notable for the young age of the afflicted patients the totipotent capacity for differentiation of the tumor cells and its curability about 95 of newly diagnosed patients are cured. Experience in the management of GCTs leads to improved outcome. Incidence and Epidemiology In 2007 7920 new cases of testicular GCT were diagnosed in the United States the incidence is decreasing after having increased slowly over the past 40 years. The tumor occurs most frequently in men between the ages of 20 and 40. A testicular mass in a male 50 years should be regarded as a lymphoma until proved otherwise. GCT is at least four to five times more common in white than in African-American males and a higher incidence has been observed in Scandinavia and New Zealand than in the United States. Etiology and Genetics Cryptorchidism is associated with a severalfold higher risk of GCT. Abdominal cryptorchid testes are at a higher risk than inguinal cryptorchid testes. Orchiopexy should be performed before puberty if possible. Early orchiopexy reduces the risk of GCT and improves the ability to save the testis. An abdominal cryptorchid testis that cannot be brought into the scrotum should be removed. About 2 of men with GCTs of one testis will develop a primary tumor in the other testis. Testicular feminization syndromes increase the risk of testicular GCT and Klinefelter s syndrome is associated with mediastinal GCT. An isochromosome of the short arm of chromosome 12 i 12p is pathognomonic for GCT of all histologic types. Excess 12p copy number either in the form of i 12p or as increased 12p on aberrantly banded marker chromosomes occurs in nearly all GCTs but the gene s
