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 ciliary ...

of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

. 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 (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...

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

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...

Signs and Symptoms

The most common symptoms of diktyoma are

vision loss Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficul ...

and pain, while the most common signs are leukocoria and presence of a mass in the

iris Iris most often refers to: *Iris (anatomy), part of the eye * Iris (color), an ambiguous color term *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (given name), a feminine given name, and a list of peopl ...

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 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 luxated lens ...

glaucoma Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of ...

cataract A cataract is a cloudy area in the lens (anatomy), lens of the eye that leads to a visual impairment, decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or ...

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 an eye disorder in which the eyes do not properly align with each other when looking at an object. The eye that is pointed at 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; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malig ...

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

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 ...

nuclear pleomorphism Pleomorphism is a term used in histology and cytopathology to describe variability in the size, shape and staining of cells and/or their nuclei. Several key determinants of cell and nuclear size, like ploidy and the regulation of cellular metab ...

, markedly abnormal mitotic activity, sarcomatous components, or invasion into the

uvea The uvea (; derived from meaning "grape"), also called the uveal layer, uveal coat, uveal tract, vascular tunic or vascular layer, is the pigmented middle layer of the three concentric layers that make up an eye, precisely between the inne ...

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

, 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 eye containing mainly collagen and some crucial elastic fiber. In the development of t ...

. Most diktyomas are malignant.

Imaging findings

Imaging studies such as

ultrasonography Medical ultrasound includes diagnostic techniques (mainly imaging) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, muscles, joints, ...

(US),

Computerized Tomography A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

(CT) and

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

(MRI) may aid

diagnosis Diagnosis (: diagnoses) is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in a lot of different academic discipline, disciplines, with variations in the use of logic, analytics, and experience, to determine " ...

. 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, diktyomas 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 consequenc ...

s in the teratoid type. On MRI, diktyomas 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 hum ...

.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 80% of retinoblastoma cas ...

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. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

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 The basement membrane, also known as base membrane, is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between epithelial tis ...

associated with the vitreous forms the

internal limiting membrane The internal limiting membrane, or inner limiting membrane, is the boundary between the retina and the vitreous body, formed by astrocytes and the end feet of Müller cells Müller may refer to: Companies * Müller (company), a German multinati ...

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 heteroplastic 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 ...

, rhabdomyoblasts, 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 oth ...

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

is no longer done due to risk of late complications and metastases. Small lesions can be treated with iodine-125 plaque

brachytherapy Brachytherapy is a form of radiation therapy where a sealed radiation, radiation source is placed inside or next to the area requiring treatment. The word "brachytherapy" comes from the Ancient Greek, Greek word , meaning "short-distance" or "s ...

. 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 astro ...

(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