Ординатура / Офтальмология / Английские материалы / Orbital Tumors Diagnosis and Treatment_Karcioglu_2005

away from the wall. During this procedure, it is important to look for areas of firm connection between the dermoid wall and the bone, which may represent vestigial portions of the originally entrapped epidermis. If these adherences are left behind, the likelihood of recurrence increases. Application of the cryoprobe during the dissection is suggested by some authors; however, the cryoprobe is usually not necessary for the excision of superficial lesions that readily present themselves. The effectiveness of the cryoprobe to adhere itself to a deeper dermoid is limited; because of the fatty content of the cyst, only a superficial iceball is created between the tip of the probe and the wall of the lesion. At times the cryoprobe may very well be a disadvantage because if applied to a weak portion of the wall, it may create a break in the capsule and make the intact removal more difficult.

The surgical removal of deep orbital dermoids is more difficult.32 The decision to remove these lesions depends on the size and location of the tumor and its potential to lead to functional deficit. If the tumor compresses the globe and the optic nerve or causes extraocular motility disturbance, which in turn leads to amblyopia, removal is indicated and should be done without delay. The rule just given for the removal of

superficial dermoids applies to deep orbital lesions, as well: that is, the surgeon should first attempt to remove the lesion with an intact capsule. However, in deep lesions, this is not as easy as with superficial ones because of limited visibility, presence of vital structures adjacent to the lesion, and the possible adherence of the base of the long-standing lesion to the bone. In these situations, if the lesion cannot be removed in toto, the luminal contents may be removed carefully without too much spillage into the soft tissues. Once the cyst wall has been opened and the contents completely cleaned, it may be easier to mobilize the lesion for removal from its bony attachments. If the lesion is too large and extends into adjacent cavities including the nose, paranasal sinuses, and the cranium, removal of the lesion through orbital surgery alone may be impossible; treatment in such cases should be undertaken jointly with ear, nose, and throat surgeons and neurosurgeons.

DERMOLIPOMA

Dermolipoma is another choristomatous lesion that contains skin and adnexal elements surrounded by a

C H A P T E R 2 5 : B E N I G N

disproportionate amount of fat within conjunctival, episcleral, and anterior orbital tissues. These lesions are not cystic. Because of the superiolateral location of these lesions, the lacrimal gland, its ductules, and the lateral rectus muscle may be affected by sufficiently large dermolipomas (Figure 25.6). Most of these lesions in children are discovered accidentally by parents; a common presentation is as a yellowish-white superiotemporal mass partially covered with a thin web of blood vessels.

Dermolipomas are frequently associated with a number of congenital developmental disorders including Goldenhar syndrome, Treacher–Collins syndrome, hemifacial microsomia, and linear nevus sebaceous syndrome.33–36 Unless dermolipomas reach a very large size, enough to distort the eyelid anatomy, or unless they contain hairs on their surface that cause persistent foreign body sensation, they should be observed and managed conservatively.37,38 Even when surgical management is elected, partial excision of the symptomatic portion should be employed rather than complete resection of the tumor. Serious complications have been reported as a result of overzealous dermolipoma excisions, including damage to the palpebral lobe of the lacrimal gland and its ductules, as well as strabismus and pseudostrabismus.39,40 With a conservative approach, serious complications such as extraocular disturbance with diplopia, upper eyelid ptosis, and dry eyes are likely to be avoided.

Other lesions that can be encountered in the superior lateral fossa include complex choriostomas, which are made of a variety of ectopic tissues including lacrimal gland, conjunctival, and respiratory tract epithelium as well as central nervous system tissue.41–47 Cystic dilatation of the lacrimal gland ductules known as dacryops may also present as space-occupying lesions in the lacrimal fossa (Figure 25.7).48,49 Dacryops may occasionally present as a congenital lesion (Figure 25.8).

FIGURE 25.6. A dermolipoma of the left superior orbit and periocular tissues (black arrow) in an adult. The lacrimal glands are marked with white arrows bilaterally. The patient had had this lesion since childhood.

FIGURE 25.7. (A) Slit lamp view and (B) axial CT image of dacryops reveal its thin, transparent wall (arrows). (C) Histopathologic appearance shows the distended dacryops (dy) lumen lined by two layers of columnar epithelium and containing a small amount of pinkish proteinaceous material. Partially atrophic lacrimal gland acini (lg) are scattered around the distended ductule.

TERATOMA

Teratoma is a germ cell tumor that contains tissues derived from the endoderm, ectoderm, and mesoderm (Figure 25.9).50,51 Therefore, these lesions may contain skin, bowel, lung, brain, thyroid, cartilage, and bone tissues. Most teratomas develop unilaterally and in girls. A great majority of these congenital tumors are benign. Occasional reports have documented malignant transformation within orbitocranial teratomas. These tumors continue to grow 6 to 12 months after birth because of the collection of secretions from different tissues into the partially cystic spaces of the tumor. Some teratomas create massive proptosis, and most can be treated only by exenteration. Recently, however, some of these lesions have been removed surgically, with preservation of the globe and other vital orbital structures reported.52

If the teratoma extends beyond the orbit into the cranium, radical surgical efforts including craniotomy are indicated.53 Although most orbital teratomas are small, some reach alarming sizes with marked distortion of the craniofacial anatomy. Large teratomas may displace the globe severely, to the degree that the tumor may be completely invisible, with total loss of vision secondary to compression of the globe and/or the optic nerve. These lesions may be solid or cystic, and the cystic ones tend to grow because of the accumulation of secretory elements within the cysts of the teratoma. In a great majority of the cases, the growth of

the lesion is not caused by malignant behavior; however, recurrence and malignant transformation have been reported in incompletely excised teratomas.54,55

MASS LESIONS SECONDARY TO ORBITOCRANIAL MALDEVELOPMENTS

Cephalocele results from the herniation of maldeveloped tissues of the central nervous system (CNS), in-

cluding meninges (meningocele), brain parenchyma (encephalocele), and the combination of the two (meningoencephalocele) into the orbital cavity.44,56 Intraorbital cephaloceles may develop anteriorly at the suture lines of orbital bones or posteriorly extending into the orbit from orbital fissures and the optic canal. Depending on the combination of these herniations, they contain brain and/or meningeal tissues (Figures 25.10 and 25.11). Herniation of the CNS tissue and meninges into the orbit occurs with a high incidence

FIGURE 25.9. Orbitocranial teratomas may reach incredibly large size to the point of distorting the craniofacial anatomy. (A,B) Teratomas that had successful surgical procedures without any recurrence. (C,D) Teratomas may contain different types of tissues in-

cluding intestinal mucosa (white arrows), glandular tissue (glnd), cartilage (crt) and (cyst) intermixed with fibrous tissue and blood vessels (black arrows).

among children with congenital craniofacial clefting abnormalities.36 Orbital meningoencephaloceles are considered to be developmental abnormalities that occur secondary to the lack of fusion or delayed fusion between orbital bones.

Anterior meningoencephalocele most commonly herniates through an opening between the frontal and

FIGURE 25.10. (A,B) Superiorly located, partially calcified encephalocele causing inferior dislocation of the left eye and blepharatosis of the left upper eyelid. The left globe was prephthisical at the time of presentation, with total disorganization of its internal structure and partial calcification. (C) The combined A and B scans show the disorganized globe with multiple calcified foci causing the spikes on A scan. (D) The bluish-purple, glossy surface of the encephalocele after removal. Inset: Histopathologic appearance of the encephalocele showing brain tissue with focal calcifications.

lacrimal bones, which characteristically presents shortly after birth. The mass clinically presents as a fluctuant bluish lesion between the nose and the medial canthal. On palpation, these lesions are felt to be softer than other developmental cysts.57 The globe and the lacrimal drainage system are usually displaced laterally, and some patients may have epiphora.58

FIGURE 25.11. (A) A large, partially cystic meningoencephalocele occupying the posterior orbit and causing axial proptosis. (B–D) Histopathologic photographs from different parts of the same lesion show haphazard coexistence of different types of tissue, including brain (b), meninges (m), and fat (f). Some of the cystic lesions are lined by ciliated ependymal

cells (e).

When the meningoencephalocele is posteriorly located, it usually herniates through the superior orbital fissure and/or optic canal. The symptoms of the posterior meningoencephalocele are less dramatic than those of its anterior counterpart. It usually presents with slowly progressive proptosis, and displacement of the globe and extraocular motility disturbances. Both anterior and posterior meningoencephaloceles may present with pulsating proptosis, depending on the size of the bony defect. In some instances, the pulsation ceases because fibrosis or fusion of the bony defect has cut off the CNS tissue herniation from its connection to the brain, and the lesion becomes an isolated orbital mass. Aberrant fibroglial tissue has also been described in the orbit.59

Grossly, meningoceles and meningoencephaloceles are well-circumscribed masses that appear to be grayish-white and glistening on the cut surface. Histopathologic examination may or may not reveal meningeal tissue around the herniated mass. The mass itself is usually composed of brain tissue that sometimes contains tiny calcified psammoma bodies.

The osseous defect can usually be demonstrated by CT, which is the most useful imaging study. The connection of the encephalocele contents to the brain tissue may also be demonstrated with CT and MRI. The

treatment of orbital cephaloceles demands a multidisciplinary surgical approach, primarily relying on the input of neurosurgeons and craniofacial surgeons.60,61

CONGENITAL CYSTS

Anophthalmos/Microphthalmos

When the globe is abnormally developed, microphthalmos, congenital cystic eye and, extremely rarely, anophthalmos occur. Microphthalmos is usually seen as a unilateral condition; in about 10% of cases it is associated with other craniofacial malformations, including agenesis of the corpus callosum, polymicrogyria, and midline arachnoidal cysts. Microphthalmos may be seen as a part of several genetically determined neuronal migration disorders such as Walker–Warburg syndrome, Aicardi syndrome, and Fukuyama congenital muscular dystrophy.

In microphthalmos and anophthalmos, the orbit may be well formed at birth but does not develop to a full adult volume because of the abnormal eye and/or cyst formation (Figure 25.12). The mechanism by which the presence of the globe affects the growth of the orbit is not well understood.62,63 This cystic struc-

ture may increase rapidly in size to overshadow the abnormal globe, leading to potential confusion with a neoplasm. When cystic lesions in the orbit are suspected, imaging studies should be performed—not only to look for other intracranial abnormalities but also to establish the possible connection of the cyst to the colobomatous globe and/or to abnormally formed meninges.64

The size of the cyst varies depending on the degree of embryonic maldevelopment. The early failure of the closure of the embryonic optic fissure leads to large colobomatous defects with a large congenital cystic component, easily identified at birth (Figure 25.13).65 The larger the cyst at birth, the smaller and more abnormally developed is the globe. These congenital cysts are commonly unilateral; but bilateral cysts have been reported in association with 131 deletion syndrome and trisomy 18.66,67 The degree of proptosis is usually moderate, with an anterior superior displacement of the globe. Examination with transillumination and B-scan ultrasonography can help to differentiate these lesions from solid congenital mass lesions, including teratomas and cephaloceles. Imaging with CT and MR will confirm the presence of the cyst and establish the position of the cyst within the orbit in relation to the abnormal globe.68,69 CT is also useful to identify any associated bony abnormalities of the orbit.

FIGURE 25.13. (A,B) A microphthalmic, maldeveloped right eye with a colobomatous cyst (c). Note the inferiorly located cyst formation with thin, purplish-blue overlying skin. These cysts usually transilluminate well with a muscle light.

Most of the microphthalmic eyes have a poor visual prognosis. If they are accompanied with large cysts, the best treatment is enucleation with complete excision of the cyst. Smaller cysts associated with a reasonably well-developed globe, which may continue to grow and maintain the growth of the orbit, may not require enucleation. Instead, the orbital cyst is excised by itself.70

The differential diagnosis of the congenital medial cystic mass should also include dacryocystocele; rarely, encepholocele and the lacrimal drainage system malformations may occur together.71

OTHER CYSTS

Mucocele

Orbital mucocele is a rare lesion in the pediatric age group. Most mucoceles in children originate from the ethmoid sinuses, as opposed to the common occurrence of the adult mucocele from the frontal sinus. This is most likely due to delayed formation of the frontal sinus, which begins to aerate around the age of 10. Mucocele is covered in detail elsewhere in the book (see Chapter 29). It should be kept in mind that pediatric orbital mucoceles may develop into common pediatric disorders of children: allergic rhinitis and cystic fibrosis.72,73 The treatment is surgical drainage and removal, which can occasionally be done endoscopically.74,75

Arachnoidal Cyst

The arachnoidal cyst is a rare, benign distension of the meningeal tissues, which surround the optic nerve.76,77 Histopathologically, the wall consists of dura and epidural tissue with proliferation of the underlying meningothelial cells.77 This lesion may be encountered in all age groups and presents with compressive optic neuropathy with decreased visual acuity and visual field loss due to atrophy of the optic nerve. Cystic masses of the optic nerve sheath have also been reported to develop as a result of trauma.78

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Based on several large series published during the past three decades, the incidence of orbital malignancies in children and adolescents ranges from approximately 8 to 18% of all orbital lesions in this age group.1–6 The most common orbital malignancy in the United States and western European series is rhabdomyosarcoma, which accounts for approximately 40% of all pediatric orbital malignant tumors. In the developing countries and the underdeveloped regions of the world, however, the most common orbital malignancies in the pediatric group are not primary malignant tumors, but secondary and metastatic lesions, such as retinoblastoma, Burkitt’s lymphoma, and leukemias.7–10 Other tumors, including mesenchymal malignancies (Ewing’s sarcoma, osteogenic sarcoma, fibrosarcoma, alveolar soft part sarcoma, malignant hemangiopericytoma), fibrohistiocytoses (Langerhans cell histiocytosis), lacrimal gland tumors (adenoid cystic carcinoma), and secondary metastatic tumors (neuroblastoma and esthesioneuroblastoma) also develop within the pediatric orbit, leading to proptosis, extraocular motility disorders, and compressive optic neuropathy. Although it is a low-grade malignancy, optic nerve glioma (grade I and II astrocytoma) should also technically be considered to be a ma-

lignant lesion of the pediatric orbit.

This chapter details the more commonly encountered primary and secondary malignant tumors of the pediatric orbit, including rhabdomyosarcoma, orbital myeloid sarcoma (granulocytic sarcoma), neuroblastoma, and the optic nerve glioma. Other tumors, listed by way of introduction, are covered elsewhere in this book (Chapters 5, 15, 17, 18, and 22).

PRIMARY TUMORS

Orbital Rhabdomyosarcoma

Once considered to be a very rare malignancy, orbital rhabdomyosarcoma (RMS) has emerged as the most common malignant mesenchymal orbital tumor of childhood. It accounts for about 5% of all cancers in the pediatric population. Rhabdomyosarcoma of the neck and the head usually appears in the first decade of life.

Orbital RMS accounts for about 10 to 20% of all the rhabdomyosarcomas. Males are more affected than females, and the mean age at diagnosis is 8 years. A history of trauma is frequently associated with the clinical presentation of the tumor.11,12 The histopathologic types include embryonal, alveolar, spindle cell, and botryoid tumors (Box 26.1). The embryonal type is the most common; the alveolar is less common and carries the worst prognosis (Figures 26.1 and 26.2).13 Another type of RMS, called the pleomorphic type, is extremely rare in the orbit. Tumor location correlates with histology: embryonal and differentiated types are more commonly located in the superonasal quadrants, whereas the alveolar type originates within the inferior orbit.14

Orbital RMS can present insidiously, mimicking other lesions clinically and radiologically. The most characteristic presenting features of orbital RMS are a fairly rapid onset and progression of proptosis and displacement of the globe (Box 26.2). The upper inner quadrant is the most common site of origin. Intracranial extension and invasion of the paranasal sinuses are rather uncommon at presentation, whereas changes in the adjacent bone have frequently been reported.15

The best way of arriving at a diagnosis is to suspect rhabdomyosarcoma whenever one observes the clinical presentation of a rapidly progressive unilateral exophthalmos in a child. However, RMS may also present as a palpable nodular subconjunctival or lid mass with edema of the lids and conjuctiva (Figure 26.3). Symptoms depend on the origin and site of the tumor mass. Posterior tumors rapidly develop edema of the optic disk, choroidal folds, and some degree of ophthalmoplegia (Figure 26.4). When RMS is situated in the inferior and anterior portions of the orbit, it often causes obvious chemosis and swelling of the eyelids. The superior nasal quadrant of the orbit is the most common site of origin of this tumor.13

Once ophthalmologists believed that orbital RMS arose from the extraocular muscles; now, however, it is accepted that the condition develops from undifferentiated mesenchymal cells that have the capacity to differentiate into striated muscle.16 The clinical differential diagnosis includes most causes of proptosis in childhood. The important lesions to be considered