Medulloepithelioma - Causes, Clinical Findings, Diagnosis, and Treatment

Introduction:

Every eye consists of a ciliary body, a ring-like structure between the choroid (vascular layer) and iris (colored portion) of the eye. The main function of the ciliary body is to change the shape of the lens to aid the eye in focusing; also, it produces a fluid called aqueous humor.

The ciliary body mainly consists of the following:

• Ciliary muscle - It contracts to help in focusing images.

• Ciliary processes - It aids in eye accommodation by attaching to the lens.

• Ciliary epithelium - It comprises outer and inner layers. The outer or pigmented layer consists of melanin granules, whereas the inner layer is non-pigmented and helps make aqueous humor.

What Is Medulloepithelioma?

The rare tumor arising from the non-pigmented inner layer of the ciliary body is referred to as medulloepithelioma. Rarely, it also arises from the retina or optic nerve of the eye. The tumor appears gray, white, or yellow and usually develops in childhood between 2 years to 10 years. The tumor grows slowly and spreads to nearby tissues (locally invasive).

How Is Medulloepithelioma Classified?

Medulloepithelioma is the common tumor of the non-pigmented ciliary epithelium (NPCE). According to Zimmerman, it is classified as:

• Teratoid medulloepithelioma - It is more common, and it comprises cells similar to that of the ciliary epithelium.

• Non-teratoid medulloepithelioma - It is less common than the teratoid type, consisting of cells similar to those of brain and cartilage tissue.

• Both types are classified again as benign (non-cancerous) and malignant (cancerous) according to their clinical features.

What Causes Medulloepithelioma?

The exact cause of medulloepithelioma is not known. It occurs suddenly and is non-hereditary. In rare cases, it arises in association with retinoblastoma (a malignant tumor of the retina).

What Are the Common Symptoms?

The classic symptoms in individuals with medulloepithelioma are:

• Painful eyes.

• Poor vision.

• Leukocoria - The round hole in the colored part of the eye is known as the pupil. It usually looks black, but in leukocoria, the pupil looks white.

• Strabismus - A condition in which both eyes point in different directions.

What Are the Clinical Findings?

The features that are observed during clinical examination include the following:

• Increased intraocular pressure.

• Glaucoma - It is an eye condition that damages the optic nerve due to raised eye pressure.

• Cataract - The clear lens of the eye becomes clouded due to protein build-up.

• Presence of grayish-white mass in the iris.

• Lens coloboma - It is a defect in the lens shape.

• Lens subluxation (dislocation of the lens).

• The whitish-pink appearance of the ciliary body.

• Calcifications (chalky-white deposits on the ciliary body).

• Ectropion uveae - It is a rare condition where the posterior pigmented layer of the iris is present on the front surface of the iris.

• Iris neovascularization - It is the development of new blood vessels on the iris.

• Uveitis - It is the inflammation of the middle layer (uvea) of the eyewall.

• Hyphema - It is characterized by the collection of blood in the front (anterior chamber) of the eye.

• Vitreous hemorrhage - It refers to the leakage of blood around the vitreous cavity.

• Retinal detachment - The inner layer of the eye (retina) is detached from its normal position.

How Is Medulloepithelioma Diagnosed?

• Magnetic Resonance Imaging (MRI): It provides a detailed image of the tumor. Characteristic features like coloboma and lens displacement are visualized. The spread of the tumor to the nearby tissues is also identified using MRI.

• Ultrasound Imaging: Ultrasound B-scan is used to detect the presence of mass or any abnormalities in the intraocular structures. High-frequency sound waves are transmitted to the eye, and the signals obtained are converted into images. The calcification in the tumor also provides dense echoes on ultrasound examination similar to that of retinoblastoma. An ultrasound biomicroscopy (UBM) is another technique to detect the size and location of smaller tumors, especially in the anterior portion of the eye.

• Fluorescein Angiography: A special dye is administered in the bloodstream to examine the blood vessels and blood flow in the eye. The development of new blood vessels in the iris is visualized in patients with medulloepithelioma.

What Is the Differential Diagnosis?

The conditions that comprise features similar to medulloepithelioma are discussed below:

• Coats Disease: It is characterized by the improper development of retinal blood vessels. Features like poor vision, strabismus, glaucoma, cataract, etc., are similar to medulloepithelioma. However, the differentiating feature is the absence of calcification in Coats disease.

• Juvenile Xanthogranuloma: It is a common skin disorder that causes skin lesions in early childhood. It also affects the iris of the eye, leading to complications like glaucoma, hyphema, etc.

• Retinoblastoma: It is a tumor arising from the retina. It is found that 40 % of the children acquire it from their parents. The features include strabismus, white pupil, etc. The imaging also shows the presence of calcifications similar to medulloepithelioma. It is differentiated by the lack of cysts in retinoblastoma.

How to Treat Medulloepithelioma?

• Enucleation: It is the most commonly used surgery in the case of advanced medulloepithelioma. It involves the complete removal of the eye from its socket (orbit). In a few cases, the surrounding tissues or fascia is also surgically excised.

• Local Resection: It involves the removal of the tumor and surrounding tissue. But, the chances of recurrence are high after local resection. Later, it is then followed by an enucleation procedure.

• Plaque Brachytherapy: It is the method of delivering high radiation doses to the tumor. It is used in treating small to medium-sized tumors. The patients are followed-up to detect any spread of a tumor to the surrounding tissues.

• Chemotherapy: Drugs like Cyclophosphamide, Vincristine, and Carboplatin are used along with radiotherapy and surgery. The effect of chemotherapy alone in treating medulloepithelioma is still under investigation.

Conclusion:

Medulloepithelioma is a rare tumor that develops in children. The prognosis depends on the spread of the tumor and the treatment modality. The survival rate is found to be increased after the enucleation procedure. It is often misdiagnosed and treated for specific clinical features like glaucoma and cataracts. Therefore, specialists' knowledge is required to diagnose the tumor properly and provide appropriate treatment.