出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/30 15:26:46」(JST)
| Testicular cancer | |
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7.4 × 5.5-cm seminoma in a radical orchiectomy specimen.
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| Classification and external resources | |
| Specialty | Oncology |
| ICD-10 | C62 |
| ICD-9-CM | 186.9 |
| OMIM | 273300 |
| DiseasesDB | 12966 |
| MedlinePlus | 001288 |
| eMedicine | med/2250 med/863 |
| MeSH | D013736 |
Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system.
Not all lumps on the testicles are tumors, and not all tumors are malignant (cancerous). There are many other conditions, such as testicular microlithiasis, epididymal cysts, and appendix testis (hydatid of Morgagni), which may be painful but are non-cancerous.
Testicular cancer has one of the highest cure rates of all cancers with an average five-year survival rate of 95%.[1] If the cancer has not spread outside the testicle, the 5-year survival is 99% while if it has grown into nearby structures or has spread to nearby lymph nodes, the rate is 96% and if it has spread to organs or lymph nodes away from the testicles, the 5-year survival is around 74%.[2] Even for the relatively few cases in which cancer has spread widely, chemotherapy offers a cure rate of at least 80%.[3]
Globally testicular cancer resulted in 8,300 deaths in 2013 up from 7,000 deaths in 1990.[4] In the United States, about 8,000 cases are diagnosed a year.[5][6] In the UK, approximately 2,000 men are diagnosed each year,[7] and over his lifetime, a man's risk of testicular cancer is roughly 1 in 200 (0.5%).[8] It is the most common cancer in males aged 20–39 years, the period when it is most common to start, and is rarely seen before the age of 15 years.[9]
One of the first signs of testicular cancer is often a lump or swelling in the testes. The U.S. Preventive Services Task Force (USPSTF) recommends against routine screening for testicular cancer in asymptomatic adolescent and adults including routine testicular self-exams.[10] However, the American Cancer Society suggests that some men should examine their testicles monthly, especially if they have a family history of cancer, and the American Urological Association recommends monthly testicular self examinations for all young men.[11][12]
Symptoms may also include one or more of the following:
It is not very common for testicular cancer to spread to other organs, apart from the lungs. If it has, however, the following symptoms may be present:
Most testicular germ cell tumors have too many chromosomes, and most often they are triploid to tetraploid. An isochromosome 12p (the short arm of chromosome 12 on both sides of the same centromere) is present in about 80% of the testicular cancers, and also the other cancers usually have extra material from this chromosome arm through other mechanisms of genomic amplification.[15]
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The main way testicular cancer is diagnosed is via a lump or mass inside a testis. More generally, if a young adult or adolescent has a single enlarged testicle, which may or may not be painful, this should give doctors reason to suspect testicular cancer.
Other conditions may also have symptoms similar to testicular cancer:
The nature of any palpated lump in the scrotum is often evaluated by scrotal ultrasound, which can determine exact location, size, and some characteristics of the lump, such as cystic vs solid, uniform vs heterogeneous, sharply circumscribed or poorly defined. The extent of the disease is evaluated by CT scans, which are used to locate metastases.
The differential diagnosis of testicular cancer requires examining the histology of tissue obtained from an inguinal orchiectomy - that is, surgical excision of the entire testis along with attached structures (epididymis and spermatic cord). A biopsy should not be performed, as it raises the risk of spreading cancer cells into the scrotum.[citation needed]
Inguinal orchiectomy is the preferred method because it lowers the risk of cancer cells escaping. This is because the lymphatic system of the scrotum, through which white blood cells (and, potentially, cancer cells) flow in and out, links to the lower extremities, while that of the testicle links to the back of the abdominal cavity (the retroperitoneum). A transscrotal biopsy or orchiectomy will potentially leave cancer cells in the scrotum and create two routes for cancer cells to spread, while in an inguinal orchiectomy only the retroperitoneal route exists.
Blood tests are also used to identify and measure tumor markers (usually proteins present in the bloodstream) that are specific to testicular cancer. Alpha-fetoprotein, human chorionic gonadotropin (the "pregnancy hormone"), and LDH-1 are the typical tumor markers used to spot testicular germ cell tumors.
A pregnancy test may be used to detect high levels of chorionic gonadotropin, however the first sign of testicular cancer is usually a painless lump.[16] Note that only about 25% of seminomas have elevated chorionic gonadotropin, so a pregnancy test is not very sensitive for making out testicular cancer.[17]
After removal, the testicle is fixed with Bouin's solution[18][19] because it better conserves some morphological details such as nuclear conformation. Then the testicular tumor is staged by a pathologist according to the TNM Classification of Malignant Tumors as published in the AJCC Cancer Staging Manual. Testicular cancer is categorized as being in one of three stages (which have subclassifications). The size of the tumor in the testis is irrelevant to staging.[20] In broad terms, testicular cancer is staged as follows:
Further information on the detailed staging system is available on the website of the American Cancer Society.[22]
Although testicular cancer can be derived from any cell type found in the testicles, more than 95% of testicular cancers are germ cell tumors (GCTs). Most of the remaining 5% are sex cord-gonadal stromal tumours derived from Leydig cells or Sertoli cells. Correct diagnosis is necessary to ensure the most effective and appropriate treatment. To some extent, this can be done via blood tests for tumor markers, but definitive diagnosis requires examination of the histology of a specimen by a pathologist.
Most pathologists use the World Health Organization classification system for testicular tumours:[23][24]
The three basic types of treatment are surgery, radiation therapy, and chemotherapy.[25]
Surgery is performed by urologists; radiation therapy is administered by radiation oncologists; and chemotherapy is the work of medical oncologists. In most patients with testicular cancer, the disease is cured readily with minimal long-term morbidity. While treatment success depends on the stage, the average survival rate after five years is around 95%, and stage 1 cancers cases (if monitored properly) have essentially a 100% survival rate (which is why prompt action, when testicular cancer is a possibility, is extremely important).
The initial treatment for testicular cancer is surgery to remove the affected testicle (orchiectomy). While it may be possible, in some cases, to remove testicular cancer tumors from a testis while leaving the testis functional, this is almost never done, as the affected testicle usually contains pre-cancerous cells spread throughout the entire testicle. Thus removing the tumor alone without additional treatment greatly increases the risk that another cancer will form in that testicle.
Since only one testis is typically required to maintain fertility, hormone production, and other male functions, the afflicted testis is almost always removed completely in a procedure called inguinal orchiectomy. (The testicle is almost never removed through the scrotum; an incision is made beneath the belt line in the inguinal area.) In the UK, the procedure is known as a radical orchidectomy.
In the case of nonseminomas that appear to be stage I, surgery may be done on the retroperitoneal/paraaortic lymph nodes (in a separate operation) to accurately determine whether the cancer is in stage I or stage II and to reduce the risk that malignant testicular cancer cells that may have metastasized to lymph nodes in the lower abdomen. This surgery is called retroperitoneal lymph node dissection (RPLND). However, this approach, while standard in many places, especially the United States, is out of favor due to costs and the high level of expertise required to perform successful surgery. Sperm banking is frequently carried out prior to the procedure (as with chemotherapy), as there is a risk that RPLND may damage the nerves involved in ejaculation, causing ejaculation to occur internally into the bladder rather than externally.
Many patients are instead choosing surveillance, where no further surgery is performed unless tests indicate that the cancer has returned. This approach maintains a high cure rate because of the growing accuracy of surveillance techniques.
Since testicular cancers can spread, patients are usually offered adjuvant treatment - in the form of chemotherapy or radiotherapy - to kill any cancerous cells that may exist outside of the affected testicle. The type of adjuvant therapy depends largely on the histology of the tumor (i.e. the size and shape of its cells under the microscope) and the stage of progression at the time of surgery (i.e. how far cells has 'escaped' from the testicle, invaded the surrounding tissue, or spread to the rest of the body). If the cancer is not particularly advanced, patients may be offered careful surveillance by periodic CT scans and blood tests, in place of adjuvant treatment.
Before 1970, survival rates from testicular cancer were low. Since the introduction of adjuvant chemotherapy, chiefly platinum-based drugs like cisplatin and carboplatin, the outlook has improved substantially. Although 7000 to 8000 new cases of testicular cancer occur in the United States yearly, only 400 men are expected to die of the disease.
In the UK, a similar trend has emerged: since improvements in treatment, survival rates have risen rapidly to cure rates of over 95%.[26]
Radiation may be used to treat stage 2 seminoma cancers, or as adjuvant (preventative) therapy in the case of stage 1 seminomas, to minimize the likelihood that tiny, non-detectable tumors exist and will spread (in the inguinal and para-aortic lymph nodes). Radiation is ineffective against and is therefore never used as a primary therapy for nonseminoma.
Chemotherapy is the standard treatment for non-seminoma when the cancer has spread to other parts of the body (that is, stage 2B or 3). The standard chemotherapy protocol is three, or sometimes four, rounds of Bleomycin-Etoposide-Cisplatin (BEP). BEP as a first-line treatment was first reported by Professor Michael Peckham in 1983.[27] The landmark trial published in 1987 which established BEP as the optimum treatment was conducted by Dr. Lawrence Einhorn at Indiana University.[28] An alternative, equally effective treatment involves the use of four cycles of Etoposide-Cisplatin (EP).
Lymph node surgery may also be performed after chemotherapy to remove masses left behind (stage 2B or more advanced), particularly in the cases of large nonseminomas.
As an adjuvant treatment, use of chemotherapy as an alternative to radiation therapy in the treatment of seminoma is increasing, because radiation therapy appears to have more significant long-term side effects (for example, internal scarring, increased risks of secondary malignancies, etc.). Two doses, or occasionally a single dose of carboplatin, typically delivered three weeks apart, is proving to be a successful adjuvant treatment, with recurrence rates in the same ranges as those of radiotherapy. The concept of carboplatin as a single-dose therapy was developed by Tim Oliver, Professor of Medical Oncology at Barts and The London School of Medicine and Dentistry.[29] However, very long term data on the efficacy of adjuvant carboplatin in this setting do not exist.
Since seminoma can recur decades after the primary tumor is removed, patients receiving adjuvant chemotherapy should remain vigilant and not assume they are cured 5 years after treatment.
Treatment of testicular cancer is one of the success stories of modern medicine, with sustained response to treatment in more than 90% of cases, regardless of stage.[30] In 2011 overall cure rates of more than 95% were reported, and 80% for metastatic disease—the best response by any solid tumor, with improved survival being attributed primarily to effective chemotherapy.[3] By 2013, according to Cancer Research UK, more than 96 per cent of the 2,300 men diagnosed each year in the U.K. were deemed cured, a rise by almost a third since the 1970s, the improvement attributed substantially to the chemotherapy drug cisplatin.[31]
For many patients with stage I cancer, adjuvant (preventative) therapy following surgery may not be appropriate and patients will undergo surveillance instead.[32] The form this surveillance takes, e.g. the type and frequency of investigations and the length time it should continue, will depend on the type of cancer (non-seminoma or seminoma), but the aim is to avoid unnecessary treatments in the many patients who are cured by their surgery, and ensure that any relapses with metastases (secondary cancers) are detected early and cured. This approach ensures that chemotherapy and or radiotherapy is only given to the patients that need it. The number of patients ultimately cured is the same using surveillance as post-operative “adjuvant” treatments, but the patients have to be prepared to follow a prolonged series of visits and tests.
For both non-seminomas and seminomas, surveillance tests generally include physical examination, blood tests for tumour markers, chest x-rays and CT scanning. However, the requirements of a surveillance programme differ according to the type of disease since, for seminoma patients, relapses can occur later and blood tests are not as good at indicating relapse.
CT scans are performed on the abdomen (and sometimes the pelvis) and also the chest in some hospitals. Chest x-rays are increasingly preferred for the lungs as they give sufficient detail combined with a lower false-positive rate and significantly smaller radiation dose than CT.
The frequency of CT scans during surveillance should ensure that relapses are detected at an early stage while minimising the radiation exposure.
For patients treated for stage I non-seminoma, a randomised trial (Medical Research Council TE08[33]) showed that, when combined with the standard surveillance tests described above, 2 CT scans at 3 and 12 months were as good as 5 over 2 years in detecting relapse at an early stage.
For patients treated for stage I seminoma who choose surveillance rather than undergoing adjuvant therapy, there have been no randomised trials to determine the optimum frequency of scans and visits, and the schedules vary very widely across the world, and within individual countries. In the UK there is an ongoing clinical trial called TRISST.[34][35] This is assessing how often scans should take place and whether magnetic resonance imaging (MRI) can be used instead of CT scans. MRI is being investigated because it does not expose the patient to radiation and so, if it is shown to be as good at detecting relapses, it may be preferable to CT. It is possible that one or more centres in Canada may join the trial in the next year or so.
For more advanced stages of testicular cancer, and for those cases in which radiation therapy or chemotherapy was administered, the extent of monitoring (tests) after treatment will vary on the basis of the circumstances, but normally should be done for five years in uncomplicated cases and for longer in those with higher risks of relapse.
A man with one remaining testis may maintain fertility. However, sperm banking may be appropriate for men who still plan to have children, since fertility may be adversely affected by chemotherapy and/or radiotherapy. A man who loses both testicles will be infertile.
Globally testicular cancer resulted in 8,300 deaths in 2013 up from 7,000 deaths in 1990.[4]
The risk of testicular cancer in white men is approximately 4-5 times the risk in black men, and more than three times that of Asian American men.[36] The risk of testicular cancer in Latinos and American Indians is between that of white and Asian men.[36] The cause of these differences is unknown.[36] Testicular cancer has the highest prevalence in the U.S. and Europe, and is uncommon in Asia and Africa.[36] Worldwide incidence has doubled since the 1960s, with the highest rates of prevalence in Scandinavia, Germany, and New Zealand.
Higher rates of testicular cancer in Western nations have been linked to use of cannabis. A study conducted by the Fred Hutchinson Cancer Research Center and funded by the National Institutes of Health, published in the journal Cancer March 15, 2009, linked long term use of cannabis to an increased risk for testicular cancer with the scientists concluding that cannabis is harmful to the human endocrine and reproductive system.[37][38][39] In September 2012, a study published in the journal Cancer became the third to link marijuana use to the development of testicular cancer.[40]
Incidence among African Americans doubled from 1988 to 2001 with a bias towards seminoma. The lack of significant increase in the incidence of early-stage testicular cancer during this timeframe suggests that the overall increase was not due to heightened awareness of the disease.
Although testicular cancer is most common among men aged 15–40 years, it has three peaks: infancy through the age of four as teratomas and yolk sac tumors, ages 25–40 years as post-pubertal seminomas and nonseminomas, and from age 60 as spermatocytic seminomas.[41]
Germ cell tumors of the testis are the most common cancer in young men between the ages of 15 and 35 years.[42]
A major risk factor for the development of testis cancer is cryptorchidism (undescended testicles). It is generally believed that the presence of a tumor contributes to cryptorchidism; when cryptorchidism occurs in conjunction with a tumor then the tumor tends to be large. Other risk factors include inguinal hernias, Klinefelter syndrome, and[43] mumps orchitis.[44] Physical activity is associated with decreased risk and sedentary lifestyle is associated with increased risk. Early onset of male characteristics is associated with increased risk. These may reflect endogenous or environmental hormones.
Testicular cancer is the 16th most common cancer in men in the UK (around 2,200 men were diagnosed with the disease in 2011). It accounts for less than 1% of cancer deaths in men (around 60 men died in 2012).[45]
Cancer is named based on where it originates, regardless of where in the body it spreads. Therefore, even if this form of cancer spreads to the lungs, it is still called and treated as testicular cancer.
Testicular tumors occur also in animals. In horses, these include interstitial cell tumors and teratomas. Typically, the former are found in older stallions (affected stallions may become extremely vicious, suggesting excessive production of androgen), and the latter are found in young horses and are large.[46]
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| リンク元 | 「精巣がん」「cancer of the testis」 |
| 関連記事 | 「test」「cancer」 |