Testicular mesothelioma is the rarest form of the cancer that develops in the tunica vaginalis, the membrane lining the testes. It has only been diagnosed in about 100 cases, accounting for less than 1 percent of all mesothelioma diagnoses.
Testicular mesothelioma, sometimes called malignant mesothelioma of the tunica vaginalis, is still a bit of a mystery to researchers overall since there have been so few cases. While there have been some studies of specific diagnosed individuals, there is still much to learn about how testicular mesothelioma develops and how doctors can expect it to progress in the body.
Asbestos and Testicular Mesothelioma
A large part of the puzzle researchers are still trying to understand is how testicular mesothelioma develops. While asbestos is a clear cause of other forms of the rare cancer, some studies have found that many of the testicular mesothelioma patients have had no known exposure to asbestos. Some studies have found that only around 41% of these diagnoses have been attributed to past asbestos exposure.
In cases of pleural mesothelioma or peritoneal mesothelioma, it’s easier to pinpoint that asbestos fibers had been inhaled or ingested and eventually became embedded into the linings of the lung or abdominal cavity. In the cases of testicular mesothelioma attributed to asbestos exposure, researchers are still unsure how the fibers make their way to the tunica vaginalis. Sometimes, these tumors may be secondary in nature and have been linked to peritoneal mesothelioma metastasis in a few cases.
Beyond asbestos exposure, researchers still have limited knowledge around the risk factors and causes of this rare form of mesothelioma. Some studies have identified that trauma, long-term hydrocele (swelling in the scrotum from fluid buildup) and a hernia or past surgery to repair a hernia should also be considered as potential causes for testicular mesothelioma. Researchers have also found that testicular mesothelioma may develop in males of any age, but those between 55 and 70 years old are most commonly diagnosed.
Diagnosing the Symptoms of Testicular Mesothelioma
Similarly to other forms of mesothelioma, most patients with testicular mesothelioma display nonspecific symptoms that may easily be attributed to other conditions and diseases, like a hernia or other testicular cancers. Doctors have also seen cases where the cancer is largely asymptomatic, and only gets diagnosed by chance following some routine physical examination.
- A lump or mass on the testicle
- Hydrocele (fluid in the scrotum causing swelling)
- Pain in the testes
- Inflammation of the epididymis (epididymitis)
Since testicular mesothelioma lacks clear, characteristic symptoms individual to the disease, doctors often first misdiagnose the cancer as an inguinal hernia. After a patient presents symptoms or an irregularity with the testicles is found on examination, a doctor may order some imaging tests, including an ultrasound.
A testicular mesothelioma ultrasound is a non-invasive, low-risk procedure that uses sound waves to create a picture of the scrotum. The ultrasound may show any swelling like hydrocele or masses that may have developed. Studies have suggested that about 56% of testicular mesothelioma patients present hydrocele, while about 33% present some solid mass in the testes.
Following an ultrasound, a doctor will likely take a blood test or assay to help determine the cause of these symptoms and hopefully detect the disease or cancer earlier. For mesothelioma specifically, there are a number of biomarkers in the blood that doctors can look for to help detect the asbestos cancer early. Doctors may look for calretinin, cytokeratin 5/6 and Wilms’ tumor gene 1 (WT1), which are often expressed by mesothelioma tumors.
Though a blood test can make a doctor more confident in a mesothelioma diagnosis, the only definitive way to diagnose the cancer is through a tissue biopsy. The biopsy will usually be the last step of the diagnostic process if a doctor suspects cancer. The biopsy will provide insight to the cell type, stage of the disease, and a patient’s prognosis.
Following a biopsy and proper diagnosis, doctors may perform additional tests to better determine if the testicular mesothelioma has spread to the lymph nodes or other parts of the body or if it is a secondary tumor to another form of mesothelioma.
Testicular Mesothelioma Prognosis
In general, researchers have found testicular mesothelioma often has a better prognosis than other forms of the disease because it is more localized. There are also several documented instances of benign mesothelioma of the tunica vaginalis. However, like with other types of mesothelioma, the cancer cells still show an aggressive growth rate and the potential to metastasize quickly.
Researchers have found the median survival is typically around 20 to 23 months, though some patients have lived years after being diagnosed. Though it might not seem like a long life expectancy, the average for other forms of mesothelioma is only about one year to 21 months.
Though the prognosis is slightly better, there is also a high risk of recurrence. One study found the recurrence rate was at least 53%, with at least 60% occurring within 2 years after successful treatment. For those with recurrent testicular mesothelioma, research suggests an average life expectancy of about 14 months.
Treatment for Testicular Mesothelioma
As with other forms of mesothelioma, this rare diagnosis is also often treated with a multimodal approach that combines surgery, chemotherapy, and radiation therapy, which will be largely determined by if the disease is still localized or has metastasized. Treatment options will be more limited as the cancer becomes more advanced.
Researchers have found that an optimal treatment for localized disease consists of a radical inguinal orchiectomy, a surgical procedure that removes one or both testicles and the spermatic cord. This surgery is considered the standard of care for all testis cancers, though there are some testis-sparing options available for some patients. Since studies have shown testicular mesothelioma often only affects one testicle when localized, a less aggressive surgery may be an option for some patients. However, one study found the recurrence rate dropped by nearly 25% for those patients who opted for the more radical surgery.
Chemotherapy alone or with radiation therapy is another option for patients who may have more advanced disease, and may sometimes be utilized in combination with surgery. Since it is so rare, researchers remain unsure of the best chemotherapy options for testicular mesothelioma. In the documented cases, most patients were treated with the standard of care, Alimta® and cisplatin. Chemotherapy in combination with radiation may also be a good option for patients who experience recurrent testicular mesothelioma.Sources
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