Mesothelioma is a cancer of mesothelial cells that are found in the covering and lining of the body’s major cavities.

The two most common places to develop mesothelioma are in the chest (pleural mesothelioma) or in the abdomen (peritoneal mesothelioma). However there are other rare forms of mesothelioma and much less is known about these forms of mesothelioma.

Mesothelioma of the testicle develops in the lining that surrounds the testicles. This lining is similar to the linings of the chest and abdomen. Mesothelioma of the testicle occurs when the disease is found in the tunica vaginalis which is a thin membrane that surrounds, protects and insulates the testicles. The tunica vaginalis is similar to the lining of the chest and abdominal cavity in that it is made up of mesothelial cells and it has two layers, a visceral (inner) layer and a parietal (outer) layer.

Incidence, causes and Presentation 
Mesothelioma of the tunica vaginalis is a very rare cancer. It accounts for only 1% of mesothelioma cases and only about 20 are diagnosed each year in the UK. The first case of mesothelioma involving the tunica vaginalis was reported in a medical journal in 1957. Most people who develop the disease are in their 50s or older and only a few are younger than 25 years.

Unlike mesothelioma found in other parts of the body there are few symptoms associated with mesothelioma of the testicle. The appearance of a lump in the scrotum is the most common presentation and this is usually caused by a hydrocele (when fluid builds up in the tunica vaginalis).

 Treatment options
As the disease is so rare, there is limited understanding of what the best treatment is for mesothelioma of the testicle. The most common treatment option involves an operation to remove the affected testicle. Other treatment options include chemotherapy or radiotherapy.

Primary pericardial mesothelioma develops in the pericardium, a membrane that lines the heart. It is one of the rarest forms of mesothelioma, accounting for 1 – 2% of all diagnoses. It is not to be confused with mesothelioma found in the pericardium that has spread from pleural mesothelioma which is far more common.

With so few cases, research is limited and conventional treatments, like surgery and chemotherapy, are often the standard course of treatment.