Testicular cancer, although an uncommon malignancy, is the most frequently occurring cancer in young men. In the year 2011, an estimated 8,290 cases of testicular cancer will have been diagnosed in the United States, with approximately 350 men succumbing to the disease. For unknown reasons, the incidence of this cancer has increased since the turn of the century, from 2 cases per 100,000 population in the 1930s, to 3.7 cases per 100,000 population from 1969 to 1971, to 5.4 cases per 100,000 population from 1995 to 1999. The greatest rise has been observed in Puerto Rico (1973 to 1997: 220%). This trend seems greatest for the development of seminoma.
Most testicular tumors are of germ-cell origin. These cancers are uniquely sensitive to chemotherapy and are considered the model for the treatment of solid tumors. Perhaps the most controversial area in the management of germ-cell tumors is the proper approach to early-stage disease (ie, surveillance vs primary retroperitoneal lymphadenectomy for nonseminomatous germ-cell tumors [NSGCTs] or radiation therapy for seminomas). In advanced disease, chemotherapy plays an essential role, but novel treatment regimens are currently being evaluated through multi-institutional clinical trials.
Epidemiology
Age
Testicular cancer can occur at any age, but it is most common between the ages of 15 and 35 years. There is a secondary peak in incidence after age 60. Seminoma is the most common histology in the older population, but it is rare in those younger than age 10.
Race
Testicular cancer is rare among blacks (1.6/100,000 population), yet black men present with higher-grade disease and have significantly worse survival at 5 and 10 years. The incidence of testicular cancer has increased in whites in the United States and Europe during the past 50 to 80 years, whereas the incidence of testicular cancer in African-Americans began to increase in the 1990s. Non-Hispanic white patients typically present with disease at early stages when compared with black, Native American, Hawaiian, and Hispanic patients.
Body size
A recent systematic review and meta-analysis of North American studies showed that testicular cancer was positively associated with adult height and a trend of inverse association with body mass index.
Geography
Denmark has the highest reported incidence of testicular cancer; East Asia has the lowest incidence of this disease.
Primary site
Germ-cell tumors present most commonly in the testes (90%) and only infrequently in extragonadal sites (10%). The most common extragonadal sites (in decreasing order of frequency) are the retroperitoneum, mediastinum, and pineal gland. Many patients presumed to have a primary retroperitoneal germ-cell tumor may have an occult germ-cell tumor of the testicle. This possibility should be evaluated with testicular ultrasonography, especially when the retroperitoneal tumor is predominantly one-sided.
Anticipated cure rates in patients with germ-cell tumors, according to disease stage
Survival
The 5-year survival rate for all patients with testicular cancer is ~95%. Cure rates are highest for early-stage disease, which is treated primarily with surgery or radiation therapy (early seminoma), and lower for advanced disease, for which chemotherapy is the primary therapy (Table 1).
Etiology and risk factors
The specific cause of germ-cell tumors is unknown, but various factors have been associated with an increased risk of this malignancy.
Prior testicular cancer
Perhaps the strongest risk factor for germ-cell tumors is a history of testicular cancer. Approximately 1% to 2% of patients with testicular cancer will develop a second primary in the contralateral testis over time. This represents a 500-fold increase in incidence over that noted among the normal male population.
The risk of contralateral testicular cancer was studied in a large population-based cohort of men diagnosed with testicular cancer before the age of 55. For 29,515 cases reported from 1973 through 2001 to the NCI's SEER Program, the 15-year cumulative risk of developing metachronous contralateral testicular cancer was 1.9%, reaffirming the practice of not performing a biopsy on the contralateral testis at initial presentation.
Cryptorchidism
Patients with cryptorchidism have a four- to eightfold increased risk of developing germ-cell tumors when compared with their normal counterparts. Orchiopexy, even at an early age, appears to reduce the incidence of germ-cell tumor only slightly. Wood and Elder conducted an extensive review of the data about cryptorchidism as it related to testicular cancer. The relative risk of testicular cancer in cryptorchidism is 2.75 to 8. A relative risk of 2 to 3 has been noted in patients who undergo orchiopexy by ages 10 to 12 years. Patients who undergo orchiopexy after age 12 or no orchiopexy are 2 to 6 times as likely to have testicular cancer.
For an undescended testis, the most common malignant histology is seminoma. For those undergoing early orchiopexy, the most common malignancy is non-seminoma. Of note, in ~10% of patients with cryptorchidism who develop germ-cell tumors, the cancer is found in the normally descended testis. Biopsies of nonenlarged cryptorchid testes demonstrate an increased incidence of intratubal germ-cell neoplasm, a presumed precursor lesion.
Genetics
Klinefelter syndrome (47XXY) is associated with a higher incidence of germ-cell tumors, particularly primary mediastinal germ-cell tumors. For first-degree relatives of individuals affected with 47XXY, approximately a 6- to 10-fold increased risk of germ-cell tumors has been observed. In addition, patients with Down syndrome have been reported to be at increased risk for germ-cell tumors. Also thought to be at greater risk are patients with testicular feminization, true hermaphroditism, persistent Müllerian syndrome, and cutaneous ichthyosis. In a genome-wide analysis of gene expression, PEPP-2 (x-linked homeobox gene), otoancorin (OTOA), and a kinase anchor protein (AKAP4) represent three candidate genes for diagnostic and therapeutic targets in testicular cancer. The International Testicular Cancer Linkage Consortium (ITCLC) has been genotyping families with multiple cases of testicular cancer and found regions on several chromosomes (3, 5, 12, 18) which are worthy of further investigation. Two new single-nucleotide polymorphism studies implicate KITLG (12p22) and SPRY4 (5q31.3) as plausible gene loci.
Family history
Of newly diagnosed patients, approximately 1.4% have a family history of testicular cancer. The risk of testicular cancer is increased 4- to 6-fold and 8- to 10-fold in sons and siblings of patients with testicular cancer, respectively.
Environment
Numerous industrial occupations and drug exposures have been implicated in the development of testicular cancer. Although exposure to diethylstilbestrol(Drug information on diethylstilbestrol) (DES) in utero is associated with cryptorchidism, a direct association between DES and germ-cell neoplasm is weak at best.
Reports have suggested an increased risk of testicular cancer among individuals exposed to exogenous toxins, such as Agent Orange and solvents used to clean jets. One author has suggested that, based on epidemiologic evidence, exposure to ochratoxin A correlated with incidence data for testicular cancer.
Prior trauma, elevated scrotal temperature (secondary to the use of thermal underwear, jockey shorts, and electric blankets), and recurrent activities such as horseback riding and motorcycle riding do not appear to be related to the development of testicular cancer.
No supporting findings substantiate a viral etiology.
Fertility
An increased risk of infertility exists for men with unilateral testicular cancer successfully treated with orchiectomy. For example, 40% of patients have subnormal sperm counts, and, by 1 year, 25% continue to have subnormal sperm counts.
