Medulloepithelioma

What medulloepithelioma is

During development, a layer of primitive cells (the medullary epithelium) forms the inner lining of the eye and parts of the brain. Medulloepithelioma arises from cells that keep this embryonic character. Under the microscope, tumors show sheets and cords resembling the developing neural tube. Some contain cartilage, muscle or other tissue (teratoid medulloepithelioma).

Intraocular (eye) medulloepithelioma

This is the more common form. It usually grows from the ciliary body, the ring of tissue behind the iris that produces eye fluid and focuses the lens.

Symptoms

• reduced vision or blurred vision in one eye
• a pink, white or gray mass visible behind or through the iris
• a white pupil (leukocoria)
• a red, painful eye, often from raised pressure (glaucoma, particularly neovascular glaucoma)
• a cloudy lens (cataract) or a notch in the lens
• an enlarged eye, tearing or light sensitivity in young children
• a squint

These signs can mimic more common problems such as congenital cataract or childhood glaucoma, which can delay diagnosis.

Diagnosis

• examination under anesthesia by a pediatric ocular oncologist
• ultrasound biomicroscopy and B-scan ultrasound to show the tumor, cysts and extent
• MRI of the eye and brain
• the diagnosis is confirmed by examining the tumor tissue after surgery; biopsy through the eye is usually avoided because of the risk of spreading tumor cells

Treatment

• Local resection: small tumors confined to the ciliary body may be removed while preserving the eye.
• Plaque brachytherapy: a small radioactive disc sewn to the eye wall for selected tumors.
• Enucleation: removal of the eye is often needed for large tumors, painful blind eyes or tumors invading surrounding tissue. An artificial eye is fitted afterward.
• Chemotherapy or radiation for tumors that have spread outside the eye.

Outlook

When the tumor is confined to the eye and fully removed, survival is excellent. Risks of a worse outcome include spread outside the eye, into the optic nerve, or malignant features. Long-term follow-up checks the other eye and the eye socket.

Brain (central nervous system) medulloepithelioma

This form is extremely rare and usually affects children under 5. Under the current World Health Organization classification, most brain tumors previously called medulloepithelioma are grouped with embryonal tumor with multilayered rosettes (ETMR), an aggressive tumor often linked to changes in a region of chromosome 19 (C19MC).

Symptoms

• headache, vomiting and drowsiness from raised pressure in the skull
• an enlarging head in infants
• seizures
• weakness, balance problems or a squint
• developmental regression

Diagnosis and treatment

Diagnosis requires MRI of the brain and spine and examination of tumor tissue with molecular testing. Treatment, at specialist pediatric brain tumor centers, combines maximal safe surgery, intensive chemotherapy (sometimes with stem cell rescue) and, depending on age, radiotherapy. Clinical trials are often offered. The outlook remains poor, although some children survive long-term.

DICER1 syndrome

Some children with ciliary body medulloepithelioma, particularly the teratoid type, carry a mutation in the DICER1 gene. This inherited syndrome also raises the risk of pleuropulmonary blastoma (a childhood lung tumor), cystic nephroma, thyroid nodules and some ovarian tumors. Genetic testing and screening are recommended for affected children and their families.

Frequently asked questions

What is medulloepithelioma?

Medulloepithelioma is a rare tumor of primitive embryonic nerve tissue, almost always found in young children. It most often grows in the ciliary body of the eye. A rarer and more aggressive form occurs in the brain.

What are the symptoms of medulloepithelioma of the eye?

Common signs include reduced vision in one eye, a visible mass behind the iris, a white pupil, a red or painful eye from raised pressure, a cloudy lens, and a squint. Because these mimic other childhood eye conditions, specialist examination is important.

Is medulloepithelioma cancer?

Many eye medulloepitheliomas are classified as malignant, but those confined to the eye and completely removed rarely spread and have an excellent outlook. Brain medulloepithelioma, now grouped with embryonal tumor with multilayered rosettes, is an aggressive cancer.

How is medulloepithelioma treated?

Small eye tumors may be removed locally or treated with plaque radiotherapy, preserving the eye. Larger tumors often require removal of the eye. Brain tumors need surgery, intensive chemotherapy and often radiotherapy at specialist centers.

Is medulloepithelioma inherited?

Most cases are not inherited, but some eye tumors are linked to DICER1 syndrome, an inherited condition that raises the risk of several other tumors. Children with medulloepithelioma are usually offered genetic testing.