Diktyoma, or ciliary body

medulloepithelioma Medulloepithelioma is a rare, primitive, fast-growing brain tumour thought to stem from cells of the embryonic medullary cavity.

, or teratoneuroma, is a rare tumor arising from primitive medullary epithelium in the

ciliary body The ciliary body is a part of the eye that includes the ciliary muscle, which controls the shape of the lens, and the ciliary epithelium, which produces the aqueous humor. The aqueous humor is produced in the non-pigmented portion of the ciliar ...

of the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. Almost all diktyomas arise in the ciliary body, although, rarely, they may arise from the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...

head or

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

. The name "diktyoma" comes from its characteristic findings on

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...

Signs and Symptoms

The most common symptoms of diktyoma are

vision loss Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

and pain, while the most common signs are

leukocoria Leukocoria (also white pupillary reflex) is an abnormal white reflection from the retina of the eye. Leukocoria resembles eyeshine, but leukocoria can also occur in animals that lack eyeshine because their retina lacks a ''tapetum lucidum''. Leuko ...

and presence of a mass in the

iris Iris most often refers to: *Iris (anatomy), part of the eye *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (color), an ambiguous color term Iris or IRIS may also refer to: Arts and media Fictional ent ...

or ciliary body.McLeanIW, Burnier MN, Zimmerman LE, Jakobiec FA. Tumors of the retina. In: Rosai J, Sobin LH, eds. Atlas of tumor pathology: tumors of the eye and ocular adnexa. Washington, DC: Armed Forces Institute of Pathology, 1994; 101–135. Other signs and symptoms include

lens subluxation Ectopia lentis is a displacement or malposition of the eye's crystalline lens from its normal location. A partial dislocation of a lens is termed lens subluxation or subluxated lens; a complete dislocation of a lens is termed lens luxation or lu ...

glaucoma Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye rem ...

cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...

exophthalmos Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Graves' disease) or unilateral (as is often seen in ...

buphthalmos Buphthalmos (plural: buphthalmoses) is enlargement of the eyeball and is most commonly seen in infants and young children. It is sometimes referred to as buphthalmia (plural buphthalmias). It usually appears in the newborn period or the first 3 mo ...

strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...

, and ptosis.

Diagnosis

Classification

Diktyoma is classified into teratoid and nonteratoid types, based on heteroplastic tissue in the former. Each type may be sub-classified as

benign Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malign ...

malignant Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

based on

. Based on histology, the tumor is classified as malignant if it contains poorly differentiated

neuroblast In vertebrates, a neuroblast or primitive nerve cell is a postmitotic cell that does not divide further, and which will develop into a neuron after a migration phase. In invertebrates such as ''Drosophila,'' neuroblasts are neural progenitor cells ...

s, nuclear pleomorphism, markedly abnormal mitotic activity, sarcomatous components, or invasion into the

uvea The uvea (; Lat. ''uva'', "grape"), also called the ''uveal layer'', ''uveal coat'', ''uveal tract'', ''vascular tunic'' or ''vascular layer'' is the pigmented middle of the three concentric layers that make up an eye. History and etymolog ...

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

, or

sclera The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and som ...

. Most diktyomas are malignant.

Imaging findings

Imaging studies such as

ultrasonography Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies fr ...

(US), Computerized Tomography (CT) and

Magnetic Resonance Imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...

(MRI) may aid

diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...

. On ultrasound, diktyomas typically appear as echogenic, irregularly shaped to ovoid masses. Ultrasound is excellent for demonstrating cystic collections of vitreous fluid in the tumor, and may show calcifications in the teratoid type. On CT, dityomas typically appear as dense, irregular masses in the ciliary body, which enhances with administration of intravenous contrast material. CT is excellent for demonstrating

dystrophic calcification Dystrophic calcification (DC) is the calcification occurring in degenerated or necrotic tissue, as in hyalinized scars, degenerated foci in leiomyomas, and caseous nodules. This occurs as a reaction to tissue damage, including as a consequence o ...

s in the teratoid type. On MRI, dityomas typically appear slightly to moderately hyperdense to vitreous on T1-weighted images and hypodense on T2-weighted images, with marked homogeneous enhancement (except for prominent parts of cystic components, which, if present, may impart heterogeneity) after administration of intravenous contrast material. MRI is excellent for detection of tumors as small as 2 millimeters.

Gross pathologic findings

Grossly, the tumor appears white, gray, or yellow, with irregular surface, often studded with small cysts. More small cysts may be found on cut sections. These cysts may break off the surface and float freely in aqueous or

vitreous humour The vitreous body (''vitreous'' meaning "glass-like"; , ) is the clear gel that fills the space between the lens and the retina of the eyeball (the vitreous chamber) in humans and other vertebrates. It is often referred to as the vitreous humor ...

.FontR, Croxatto J, Rao N. Tumors of the optic nerve and optic nerve head: medulloepithelioma. In: Silverberg S, Sobin L, eds. AFIP atlas of tumor pathology: tumors of the eye and ocular adnexa. Washington, DC: American Registry of Pathology, 2006; 148–149. The tumor may also contain chalky grayish-white particles. The lens may be covered by a semi-translucent membrane in some case. Tumor may invade locally to involve the iris or anterior retina, or through the cornea or sclera. In advanced cases, tumor may fill the entire globe, similar to

retinoblastoma Retinoblastoma (Rb) is a rare form of cancer that rapidly develops from the immature cells of a retina, the light-detecting tissue of the eye. It is the most common primary malignant intraocular cancer in children, and it is almost exclusively fo ...

Histologic findings

Microscopically, the tumor cells recapitulate embryonic sensory retina or nonpigmented ciliary epithelium. The chalky grayish-white particles within the tumor mass correspond to foci of

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

on histology; the semi-translucent membrane covering the lens in some tumors corresponds to spreading neoplastic cells. Tumor cells form a characteristic ''diktyomatous'' pattern, with folded cords and sheets resembling a fisherman's net. In early development of the retina, the medullary epithelial cells acquire polarity, such that a basement membrane associated with the vitreous forms the internal limiting membrane on one side, while terminal bars form the outer limiting membrane on the other side. Proliferating tumor cells of diktyoma maintain the same polarity, arranged in cords and sheets folding back upon themselves. Depending on the direction of the folding, some folds surround fluid collection, while others do not. These fluid-filled spaces correspond to the grossly observed small cysts, which are mainly composed of vitreous humor. About 30-50 percent of diktyomas contain heteroplastic elements, and thus belong to the teratoid subtype. These heteroplatic elements may include

hyaline cartilage Hyaline cartilage is the glass-like (hyaline) and translucent cartilage found on many joint surfaces. It is also most commonly found in the ribs, nose, larynx, and trachea. Hyaline cartilage is pearl-gray in color, with a firm consistency and has ...

rhabdomyoblast A rhabdomyoblast is a cell type which is found in some rhabdomyosarcomas. When found histologically, a rhabdomyoblast aids the diagnosis of embryonal, alveolar, spindle cell/sclerosing, and pleomorphic rhabdomyosarcomas; however, in a tumor, express ...

s, and neuroglial tissue. Sarcomatous elements may be seen in malignant tumors. Foci of dystrophic calcifications may be present.

Treatment

Diktyoma is treated by either close observation, or

enucleation of the eye Enucleation is the removal of the eye that leaves the eye muscles and remaining orbital contents intact. This type of ocular surgery is indicated for a number of ocular tumors, in eyes that have sustained severe trauma, and in eyes that are other ...

Surgical resection Segmental resection (or segmentectomy) is a surgical procedure to remove part of an organ or gland, as a sub-type of a resection, which might involve removing the whole body part. It may also be used to remove a tumor and normal tissue around i ...

is no longer done due to risk of late complications and metastases. Small lesions can be treated with iodine-125 plaque brachytherapy. Distant metastases and mortality are rare. Mortality may occur in patients with extraocular extension to the brain. Lack of glial differentiation, as demonstrated by negative staining for

glial fibrillary acidic protein Glial fibrillary acidic protein (GFAP) is a protein that is encoded by the ''GFAP'' gene in humans. It is a type III intermediate filament (IF) protein that is expressed by numerous cell types of the central nervous system (CNS), including astroc ...

(GFAP), may confer a favourable prognosis.

Epidemiology

Mean age at diagnosis is 5 years. While most cases occur in young children, adult cases have been reported. Incidence is similar in male and female and among different races.

References

External links

{{Eye tumors Ocular neoplasia