Choroid melanoma is a malignant neoplasm of the vascular membrane of the eye with a predominantly hematogenous metastasis pathway. Clinically, it is most often manifested by pain syndrome, decreased visual acuity, photopsias and metamorphopsias. Diagnostics consists of biomicroophthalmoscopy, ophthalmoscopy, fluorescence angiography, ultrasound Doppler color mapping, CT and MRI. Common methods of treating choroid melanoma are radiation therapy and enucleation. Brachytherapy with diode laser thermotherapy, endovitreal tumor removal and choroidal melanoma endoresection are also possible.
Choroid melanoma is a genetically determined tumor that develops sporadically or in individuals with a burdened family history of this disease. Choroid melanoma was first described by G. Bartisch in 1563. A detailed description of the disease in ophthalmology was presented in 1819 by the French physician Rene Laennec. According to statistics, about 70% of all malignant eye tumors are uveal melanoma. The total prevalence in the population is 9:1000000. The pathology is most often found in the Scandinavian countries, France and Israel. Neoplasia develops more often in people with light eyes. Choroid melanoma is usually diagnosed at the age of 50-60 years. Children get sick very rarely, cases of the disease in infants are casuistic. Persons of the white race are at greater risk of developing cancer, men suffer from this disease less often than women.
Often, the etiology of choroid melanoma cannot be established, since the tumor develops sporadically. There is a genetic predisposition to the development of this pathology. In 0.37% of cases, the disease is of a family nature. Triggers are mutations of the GNAQ or GNA11 gene. Pathological changes in one of the genes exclude the development of changes in the other, since with both mutations, the codon Q209 (5 exon) or R183 (4 exon) is involved in the process. A rare cause of choroid melanoma is abnormalities of the BRAF, NRAS genes. In this case, mutations of chromosome 3 (monosomy), 6 or 8 (trisomy) take place.
Significant differences in the molecular genetic profile of choroid melanoma lead to the fact that modern methods of treating melanoma of other localizations are ineffective against this form of the disease. The appearance of a pathological neoplasm is usually not preceded by changes in the vascular membrane, less often melanoma forms at the site of choroid nevus or oculodermal melanosis. Predisposing factors are blue eye color, 1 and 2 phototypes of skin according to Fitzpatrick. The negative effect of ultraviolet radiation on the development of choroid neoplasms has not been proven.
Clinical manifestations of choroid melanoma are diverse and depend on the size and type of growth of the neoplasm. There are nodular, diffuse and cup-shaped growth patterns. The tumor is more characterized by post–equatorial localization, less often – pre-equatorial or equatorial. As a rule, only one eye is involved in the pathological process. Bilateral forms occur only in 2% of patients. In most cases, the temporal parts of the choroid are affected. At the initial stages of development, melanoma of the choroid has the appearance of a small rounded formation of yellow-brown or gray color with a slight elevation. With a tumor diameter of no more than 6-7 mm, it is difficult to distinguish it from a nevus. At the same time, the disease is characterized by a latent course, often the pathology is diagnosed during a routine examination.
At the same time, the development of choroid melanoma in the central parts may be accompanied by a decrease in visual acuity, distorted perception of the shape, size or color of objects, the appearance of defects in the visual fields in the form of cattle. Episodes of photopsies are perceived by patients as “shiny balls of light” that tend to migrate from one part of the visual field to another. These phenomena occur 2-3 times a day and appear in twilight lighting. Pain syndrome in choroid melanoma is associated with the development of secondary glaucoma or uveitis.
The growth of a pathological neoplasm leads to compression of the tumor’s own veins or choroid vessels located around the melanoma. Compression of the venous apparatus is accompanied by fluid transudation, followed by the addition of an exudative component against the background of necrotic changes caused by the rapid development of the pathological process. Thus, as the size of the neoplasm increases, a local retinal detachment develops, which subsequently reaches a large extent. In the case of diffuse growth of choroid melanoma, secondary detachment may be combined with valvular rupture. At the same time, along with photopsies and metamorphopsies, patients note the appearance of black dots, “flies” or “shrouds” in front of their eyes.
Choroidal melanoma with equatorial localization is characterized by the appearance of Irwin-Gass syndrome. In the area of pathological neoplasm, the clinical picture of vasculitis and perivasculitis develops. Increased permeability of choroidal vessels leads to edema of the macular region in the distal parts. Patients complain of blurring, distortion and pink tint of the image in front of their eyes, increased sensitivity to light. In addition, with Irwin-Gass syndrome, there may be a cyclical decrease in visual acuity at certain times of the day (more often in the morning).
The most common symptoms of choroid melanoma are “fog” or floating black or red opacities in front of the eyes, photopsias and a sudden decrease in visual acuity. The development of hemophthalmos is possible. Often this pathological condition in its clinical manifestations resembles chorioretinal macular degeneration. In turn, toxic substances released during the decay of the tumor cause the development of uveitis. The frequency of inflammatory processes directly depends on the cellular composition of the tumor. Initially, in most cases, choroiditis is observed, which is the ground for the occurrence of posterior uveitis or scleritis. As a rule, inflammatory lesions of the structures of the organ of vision are detected with a diameter of melanoma of the choroid more than 15 mm and a thickness of more than 5 mm. Necrotic changes in the tumor lead to endophthalmitis or panophthalmitis. At the same time, patients complain of severe pain of the affected eye with irradiation to the eponymous half of the head, swelling and redness of the eyelids.
Choroid melanoma is one of the malignant neoplasms with a tendency to hematogenous metastasis. Metastases are most often detected in the liver and lungs, and in the terminal stages they can be detected in all organs and tissues of the body.
Diagnosis of choroid melanoma is based on anamnestic data, the results of biomicroophthalmoscopy, ophthalmoscopy, fluorescence angiography, ultrasound Doppler color mapping, computed tomography (CT) and magnetic resonance imaging (MRI). A burdened family history may indicate a hereditary predisposition to melanoma or that the oncological process is one of the manifestations of a primary multiple tumor.
The ophthalmoscopy method determines the presence of a pathological formation on the surface of the choroid, determines its size, growth pattern and shape. Choroid melanoma is often covered with druses and “fields of orange pigment”, which are represented by the deposition of lipofuscin grains. The appearance of this diagnostic criterion indicates a rapid progression of the disease. A detailed study of the surface structure of choroidal melanoma by biomicroophthalmoscopy revealed that the color of lipofuscin depends on the nature and color of the tumor. Therefore, a brown or pink-brown shade of neoplasia cannot exclude the symptom of an “orange pigment field”.
In addition, ophthalmoscopy can detect newly formed vessels with a tumor thickness of 3.5 mm or more. To detect them in the early stages of the development of choroidal melanoma, fluorescent angiography is performed. This method makes available for visualization the first signs of angiogenesis with a thickness of 1.3 mm neoplasm. With a large tumor size, the vessels look thick, short, with pronounced deformations of the structure, there is a tendency to form a chaotic network. Vascular anomalies predispose to the development of hemorrhages in the melanoma tissue of the choroid and adjacent structures of the eye, which can also be established during ophthalmoscopic examination. Ultrasound Doppler color mapping reveals retinotumoral shunts. CT and MRI are performed in the preoperative period to accurately determine the size and localization of neoplasia, as well as to detect metastases to other organs and tissues.
The tactics of treatment of choroid melanoma depends on the size, localization and prevalence of the pathological process. Methods such as radiation therapy (organ-preserving technique) and surgical intervention consisting in enucleation of the eye are used. Complete removal of the eyeball is resorted to with extensive diffuse tumor growth or a large size of nodular melanoma of the choroid. Alternative options are brachytherapy of the eye with diode laser thermotherapy, endovitreal tumor removal, melanoma endoresection and various combined techniques. Carrying out endoresection together with brachytherapy is possible even with large neoplasms. All types of surgical intervention should be performed in accordance with the principles of ablasty.
Prognosis and prevention
Specific measures for the prevention of choroid melanoma have not been developed. The prognosis for life and ability to work depends on the stage of the oncological process, the size and localization of the tumor. Mortality with a neoplasm diameter of up to 10 mm is 16%, with a diameter of more than 15 mm – 53%. For early diagnosis and treatment of choroid melanoma, it is necessary to undergo regular ophthalmologist examinations with visiometry, tonometry, ophthalmoscopy and biomicroscopy. With diffuse growth or a large diameter of the nodular shape, visual acuity is significantly reduced up to complete blindness. If it is impossible to perform an organ-sparing operation, enucleation of the eye is indicated. This surgical intervention entails the disability of the patient.