Uveal melanoma is the most common malignant tumor inside the eye in adults. The choroid forms the posterior part of the vascular skin in the eye. A choroidal melanoma is caused by a degeneration of the pigment-forming cells (melanocytes), which are important for the colour of the eye. Therefore these tumours are often dark in colour. The choroidal melanoma often metastasizes, which means that degenerated cells reach other parts of the body and accumulate there.
Frequency of uveal melanoma
Overall, eye tumours are rare compared to other tumours. Uveal melanoma affects one in 100,000 people per year in Europe. Uveal melanoma is about 50 times more common in white-skinned people than in dark-skinned people.
Uveal melanoma is a disease that is not directly hereditary or at least no direct heredity is known. Nevertheless, genetic factors can play a role. For example, people with lighter skin are more frequently affected by uveal melanoma.
In addition, certain genetic diseases such as neurofibromatosis can be a risk factor for the development of uveal melanoma. Basically, however, uveal melanoma is a disease that occurs mainly in older age and is due to many environmental factors. In most cases, choroidal melanoma initially causes no symptoms.
Therefore it remains undetected for a long time until it has reached a certain size. Sometimes it is discovered by chance during a routine examination by an ophthalmologist. When the tumour grows and reaches a certain size and has spread to the area of sharpest vision, considerable visual disturbances occur.
An orange pigment on the surface of the tumour is characteristic of a choroidal melanoma. The ophthalmologist can recognise this in his examinations. The tumour usually bulges out, sometimes with bumps.
If the doctor can detect solid tissue under the bulge during an ultrasound examination, this indicates a choroidal melanoma. The doctor can often detect a detachment of the retina in the lower part of the eye during the examination. An intense black colour and a size of less than 2 mm speak against a choroidal melanoma.
Only rarely are both eyes affected. Every routine ophthalmological examination (e.g. when prescribing glasses) should include a fundus mirror, as this allows the early detection of a choroidal melanoma. If there is a suspicion of a uveal melanoma, an ophthalmoscopy of the fundus of the eye is always indicated by the ophthalmologist, possibly even by the family doctor.
An ultrasound examination can provide information about the exact location and size of the choroidal melanoma. Abnormalities and other diseases of the choroid can be distinguished. A so-called fluorescein angiography is performed for the photographic representation of the ocular blood vessels.
In this process, the finest blood vessels are made visible by means of fluorescent dyes. This enables the doctor to get an idea of the condition of the ocular blood vessels. To exclude metastases, an X-ray of the thorax and an ultrasound examination of the abdominal organs should also be carried out.
If metastases are suspected, a computer tomography and a nuclear spin examination are recommended. A sample is also taken, a so-called biopsy, usually of the liver, if metastases are suspected. Progress and follow-up examinations are important.
The treatment of uveal melanoma depends on its size. Repeated follow-ups are recommended for a choroidal melanoma of 2-3 mm. For a size of 4-8 mm, local radiation is usually performed.
In this procedure, a radiation carrier is sewn onto the sclera of the eye and remains for a certain time, depending on the required radiation dose. However, this method is only possible if the tumour is small and of a certain size. If the tumour is larger than 8 mm, these local radiation sources cannot be used and are not effective.
For flat, small tumours, treatment with an infrared laser is possible. This is sometimes done in combination with local radiation. For small tumours, icing with the help of cold pins down to -78°, the so-called kyrotherapy, can be recommended.
Laser agitation, i.e. laser sclerotherapy, is only recommended for small tumours with a low height. In this case, the tumour is heated strongly by (laser) light. For larger tumours up to 15 mm, proton radiation is recommended.
For medium-sized tumours, radiosurgical or surgical removal of the tumour is recommended. If the tumour is in a favourable position, it can be removed from the outside. After removal of the tumour, antigen-specific stimulation of the immune system is recommended.
The aim is to remove the tumour as completely as possible and to preserve the eye. In the case of very extensive tumours, however, removal of the eye is recommended. In some cases, chemotherapy is recommended, often in combination with radiotherapy.
Here, it is possible to administer the chemotherapeutic drug directly to the blood vessels of the eye. It is also possible that the drug is introduced into the vitreous body of the eye. In both chemotherapeutic procedures, the drug is administered in high doses to the affected area.
In some cases this has improved the success of the treatment and reduced the side effects. In the past, it was suspected that excessive UV radiation might cause choroidal melanomas, similar to skin cancer (melanoma). However, since the vitreous body inside the eye absorbs the incident UV rays, UV radiation is unlikely to be the main cause of uveal melanoma.
On the other hand, a connection with the loss of one chromosome, namely chromosome 3, has been established. In contrast to skin melanoma, a close relationship to genes, a so-called genetic disposition, has been discovered in uveal melanoma. It was observed that patients with a choroidal tumour who possessed two healthy chromosomes 3 very rarely developed the malignant form of choroidal melanoma.
Correspondingly, these very rarely showed metastases. In contrast, patients with a loss of chromosome 3 very often developed malignant, metastatic choroidal melanomas. The choroidal melanoma grows for a long time without being noticed by the patient as it does not cause any symptoms.
Only above a certain size does vision become impaired. Since the choroid of the eye has no lymph vessels, the degenerated melanocytes grow without being recognized by the immune system and can form metastases in other parts of the body early in the course of the disease. Due to the lack of lymph vessels in the eye, the choroidal melanoma can grow for a very long time without being recognized by the immune system as foreign and malignant.
This is also the reason why choroidal melanomas are often already metastasized at the time of diagnosis. This means that degenerated cells of the choroidal melanoma have been transported via the blood to other parts of the body and have settled there. The most common locations of metastases in uveal melanoma are the liver and the lungs.
Since the cancer cells spread mainly via the blood, organs such as the liver, lungs and bones are usually affected. Metastases can also occur in the eye itself. The liver metastases can often be treated surgically, alternatively radiation therapy is available.
However, the prognosis in the presence of such distant metastases is still limited. The chances of recovery depend on whether the tumour could be completely removed. The further prognosis depends on various factors, including the size and cell type of the tumour tissue.
The prognosis is worse for large and so-called epitheloid-cell or mixed-cell tumours than for small and so-called spindle-cell tumours. Approximately half of those affected with epithelial or mixed-cell tumours die within 5 years. However, exceptions confirm the rule, as many individual factors determine the chances of cure and the course of the disease.
If metastases form, the prognosis is worse overall. The survival rate in uveal melanoma depends mainly on the stage at which the disease is detected. If only one tumour is found in the eye, the statistical survival rate for the next 5 years is about 75%.
In contrast, 25% of affected individuals develop metastases within the next 5 years, in which the cancer spreads to other organs. In this case the prognosis is significantly worse. If such distant metastases can already be found, the average survival is about six months.
As with many such statistically collected figures, these are average values. A reliable prediction of the survival of a single affected person is therefore not possible.