Ординатура / Офтальмология / Английские материалы / Surgical Atlas of Orbital Diseases_Mallajosyula_2009

be differentiated from prolapsed orbital fat since they are often well circumscribed, slightly more yellow, and displace orbital structures.57 (Figures 12.2A to D) They present commonly in mid-life, are more frequent in men, are not related to race, and after an initial growth phase typically do not change in size significantly.58,59 Lipomas are divided into deep and subcutaneous/superficial lesions which are much more common.

Mesenchymal Tumors 173

Lipomas are identical to subcutaneous fat on CT and MRI.17 In the orbit they can have lower density than the surrounding orbital fat simulating a cyst.57 When the tumor is encapsulated a low signal fibrous capsule may be visualized on MR and CT.17 Nonencapuslated lipomas have been reported making it difficult to localize them when adjacent to normal fat.67

174 Surgical Atlas of Orbital Diseases

Liposarcoma is one the most common soft tissue sarcomas of adult life,14 but is rare in the orbit.1,60 Thirty five cases have been reported in the literature, but misclassification is likely since our definition and pathological evaluation has improved over time.61,62 In orbital cases the average age was 64 years of age with a female predilection.55 The most common presentation is painless proptosis with an 8 month mean duration of symptoms.55 Three distinct entities have been described, each validated with cytogenetic evidence. In order of good to poor prognosis they are: well-differentiated (adipocytic, sclerosing, inflammatory, spindle cell, and dedifferentiated), myxoid/round cell, and pleomorphic.14,63 In the orbit the myxoid is the most common subtype.62 Unlike lipomas which are primarily subcutaneous in location liposarcomas are primarily deep tumors; if they occur superficially they are referred to as atypical and have an excellent prognosis since they are often amenable to complete surgical resection. It is generally believed that lipomas cannot transform into liposarcomas; the distinction in location between lipomas and liposarcomas is the primary argument cited as proof of this.14 Clinical and histopathologic diagnosis can be difficult. Treatment involves surgical excision which typically involves exenteration, although well circumscribed cases have been resected. Liposarcomas of the orbit have a favorable prognosis with no reports of a neoplasm, that meets today’s histopathological criteria for diagnosis, metastasizing and only one recurring locally.61,62

When a lesion with imaging characteristics similar to a lipoma with an adjacent non-fatty mass, liposarcoma should be added to the differential diagnosis. Liposarcomas vary from approximately a 25-75% fatty component depending on their level of differentiation.68 Liposarcomas also show calcification in approximately 12% of cases which is more common than in lipomas.17 Few papers have described the imaging in the orbit. Jakobiec et al. described central lucency due to fat seen on CT imaging resembling a cystic structure.61 They also reported that these lesions commonly involved the extraocular muscles and one case was hyperintense on MRI T1 imaging.61 A single case report described unique characteristics including an extraconal mass with MRI T2 imaging showing hypointensity in comparison to cerebral cortex and light peripheral enhancement with gadolinium.54

Lesions shown to mimic fatty tumors on imaging include myxoid tumors, lesions associated with a subacute hematoma, muscle with fatty replacement, and tumors invading surrounding fat.17

Fibrous Tissue Tumors

Despite the large number of subtypes of fibrous tumors, only a few have been reported in the orbit. Fibrosarcomas have been diagnosed much less commonly over time as our definition and pathological assessment has advanced.14 Recent series have found that they are slightly more common in men69 and usually present in the early 40’s.70, 71 Recurrence is very common occurring in approximately 45% with surgical margins being the best predictor.69 Scott et al.’s series found that recurrence occurred in 79% of tumors with inadequate margins and in 18% of those treated with wide or radical excision.69 Five year metastasis rates are around 63% and are typically to the lung, spine, and skull.69 A 5 years survival rate of approximately 40% has been reported.69 These lesions are rare as a primary tumor of the orbit but they can also invade from the nasal cavity or face. Exenteration or excision with wide local margins is recommended since they are commonly incompletely removed. CT and MR imaging typically show an aggressively infiltrating orbital mass,72 however infantile lesions have been reported to be well circumscribed.73

Solitary fibrous tumor classically occurs in the pleural lining of the lung, but has been described throughout the body including the orbit, adjacent nasal cavity and sinuses.14 Approximately 55 cases have been reported in the orbit since its first description there in 1994 with most cases being benign.74-76 It has been seen in all age groups, with a median age of 50,77 and usually presents as a wellcircumscribed yet unencapsulated lesion causing gradual proptosis.1 Pleural solitary fibrous tumor can vary greatly in its clinical characteristics and malignancy on pathological assessment. Even less is known about non-pleural solitary fibrous tumors. Approximately 10% of non-pleural lesions have been shown to recur and metastases are very rare.78 Pathological assessment for atypical features was found to be a significant predictor of recurrence.78 Since these tumors are difficult to remove due to invasion and they may undergo malignant transformation en bloc resection is recommended.79

On CT the lesions are well circumscribed and take up contrast intensely in a homogeneous or ring pattern,76 although one review suggests that contrast uptake is mild to moderate.72 With MRI these tumors also enhance intensely, commonly showing areas of hemorrhage and T2 hypointensity.72

Histiocytic Tumors Fibrous histiocytoma

Fibrous histiocytomas histologically and clinically can vary from a slowly developing benign to locally aggressive fast growing malignant lesion. Four subtypes have been described in order of frequency: storiform-pleomorphic, myxoid (myxoidfibrosarcoma), giant cell (malignant giant cell tumor of soft parts), and inflammatory (xanthosarcoma, malignant xanthogranuloma).14 Benign fibrous histiocytoma most commonly affects the skin but approximately 0.3% can occur in deeper locations such as muscle tissue.80 Recurrence rates for benign cutaneous fibrous histiocytomas following excision range from 5-10%,14,81 with deeper tumors typically presenting as a much larger lesion more often resulting in incomplete resection and thus recurrence rates have been reported closer to 50%.82,83

Malignant fibrous histiocytomas are the most common adult malignant soft tissue tumor in the body.84 Font et al.’s orbital series found that 63% were benign, 26% were locally aggressive and 11% were malignant.82 They showed that if the tumor had infiltrative margins, hypercellular zones or both, recurrence rates were 57% compared to 31% in those that did not have these features.82 Typically they are slow-growing, firm, infiltrative, and present in the upper nasal quadrant with a mean age of 43 years.82 Common presenting symptoms include proptosis (60%), mass (46%), and decreased vision (25%) with a mean duration of symptoms of 29 months.82 Complete surgical excision is recommended. This is typically accomplished by removing the tumor alone although in some infiltrative cases this might not be possible without exenteration. Recent large systemic series have reported recurrence rates from 19-21%, metastasis, mostly to lung and bone, in 31-35%, and 5 year survival rates from 65-70%. In contrast

Mesenchymal Tumors 175

ten year survival rates for orbital tumors is about 90%.1,82

It can be difficult to differentiate fibrous from other lesions.17,72 (Figures 12.3A and B) No specific ultrasonic and CT imaging characteristics have been found (Figures 12.4A to E).88 Imaging is also highly variable related to amounts of collagen, necrosis, hemorrhage, and myxoid tissue but often displays high signal intensity on T2. Benign tumors are typically well-circumscribed and may remodel bone, with malignant lesions typically having infiltrating margins and bone destruction.72 Benign histiocytomas are usually homogeneous on CT, and MRI T1 and T2 imaging, whereas malignant lesions have a more heterogeneous pattern.72 In some cases malignant lesions may have a homogeneous CT and T1 image with a heterogeneous T2 image.72 Histopathology and immunohistiochemistry help in the diagnosis (Figures 12.5A and B)

Malignant Tumors of Uncertain Type

Rhabdoid tumor is a highly aggressive neoplasm primarily seen in the kidney although it has been reported in extrarenal sites including the central nervous system and soft tissues including the orbit.14,89-96 Extrarenal sites have approximately a 15% survival, but there are too few reported cases in the orbit to come to a conclusion as to whether they behave differently than other extrarenal sites. Of the 7 described in the orbit 4 have died.

Figures 12.3A and B: (A) This 34-year-old woman presented with a history of right upper lid swelling and ptosis over 1 year, which was associated with tearing, light sensitivity and occasional sharp pain.

Physical examination findings were a palpable lacrimal gland on the right, bilateral reduced Schirmer's function, 3 mm of ptosis and 3 mm of proptosis. There was a soft nontender mass superolaterally, which was causing a 3 mm downward and 4 mm inward displacement as well as indentation of the globe, leading to elevation of macula and disc (B)

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Primary bone tumors of the orbit constitute 0.6 to 2.0% of all orbital tumors.1, 2 They can be classified into 4 main sub-groups (Table 1).3 Clinically, the commonest bone tumors encountered are osteomas, fibrous dysplasia and cholesterol granuloma.

Clinical Presentation

Bony lesions of the orbit usually present in one of three ways:3

1.Gradual proptosis and globe displacement occurring over many years secondary to a slowly progressive non-infiltrative mass effect. This is commonly seen in benign fibro-osseous tumors, such as the osteoma.

2.Sub-acute proptosis or globe displacement occurring over weeks or months which may be complicated by a sudden increase in the signs and symptoms secondary to an intralesional hemorrhage. This presentation is characteristic of reactive bone lesions.

3.Malignant bone tumors can present with infiltrative signs such as pain, restricted

movements and decreased vision occurring over weeks or months.

On radiological examination, either destruction of bone or hyperostosis is seen. It is important to note that lesions other than primary bone tumors can also cause these changes. Thus the differential diagnosis of a destructive bony lesion includes epithelial malignancies of the paranasal sinuses, bony metastases, Wegener’s granulomatosis, lymphomas, fibrosarcoma and lytic meningioma. Hyperostotic lesions may be seen in metastatic prostatic carcinoma, meningioma and osteomyelitis.

Only the three commonest lesions (osteoma, fibrous dysplasia and cholesterol granuloma) will be discussed in detail. The other conditions are briefly reviewed.

Osteoma

Osteomas are the commonest bony tumors affecting the orbit. Orbital osteomas usually arise in the frontal or ethmoidal sinus. They usually present in the fourth and fifth decades and occur equally in males and females.4

Clinically, osteomas cause gradual proptosis and globe displacement occurring over many years. There may be an associated headache and a bony mass is usually palpable in the superior or superomedial orbit. Obstruction of the sinus ostia may lead to sinusitis or mucocoele formation. Uncommon features include acquired Brown’s syndrome, gazeevoked amaurosis or pain, globe subluxation and erosion leading to orbital emphysema or CSF rhinorrhea. Osteomas of the sphenoid sinus, though rare, are important as they can cause an orbital apex syndrome and optic atrophy.3

An important systemic association is Gardner’s syndrome which is a phenotypic variant of the familial adenomatous polyposis syndrome. Gardner’s syndrome is an autosomal dominant condition whose features include colonic polyps, osteomas, and congenital hypertrophy of the retinal pigment epithelium (CHRPE). As the rate of malignant transformation of the colonic polyps is very high, screening for Gardner’s syndrome (dilated funduscopic examination and gastroenterologist referral) is recommended in patients with osteoma.5

On X-ray and CT scans, osteomas are extremely radiodense, well circumscribed lesions, usually arising in the sinus and invading the orbit. Bone windows on CT usually show a very dense periphery with a more radiolucent center.

Histologically, osteomas are composed of lamellar bone with fibrovascular stroma. They are divided into three types: ivory, compact and fibrous osteomas based on the relative proportions of lamellar bone and fibrous stroma.6 The ivory osteomas are considered to be the most mature form of the lesion. However, there does not seem to be a correlation between clinical behavior and histological subtype.3

Asymptomatic osteomas are treated conservatively, except when involving the sphenoidal sinus, as it is easier to remove a small lesion before it encroaches on the optic canal.

When symptomatic, treatment is by surgical excision. Anterior lesions are removed via an anterior orbitotomy. A modified Lynch incision may be used for superomedial osteomas. Endoscopic techniques may also be used.7 Posterior lesions may require a combined orbitocranial approach. Recurrence is rare, even following partial removal.

Bone Tumors of Orbit 181

CASE ILLUSTRATION (Figures 13.1A to D)

Fibrous Dysplasia

Fibrous dysplasia develops almost exclusively in children in the first two decades of life, though the disease may progress well into adulthood. It is a deforming but not destructive disease of bone and is caused by proliferation of fibrous tissue and osteoid in medullary bone.

Three forms are described: monostotic fibrous dysplasia accounts for most cases of orbital involvement; in polyostotic disease, deformities of long bones occur together with skull lesions; and McCune-Albright syndrome which is a triad of polyostotic fibrous dysplasia, sexual precocity and cutaneous pigmentation (with ‘coast of Maine’ borders).

Most patients present with facial asymmetry, proptosis and globe displacement progressing over many years. Associated symptoms include diplopia, anosmia, hearing defects, nasal obstruction and epiphora.8 Increased intracranial pressure and cranial nerve palsies can also occur. Extensive disease results in a deformed facies known as ‘leontiasis ossea’.

Progressive disease can result in optic nerve compression. Acute compressive neuropathy may occur secondary to intralesional hemorrhage, sphenoidal sinus mucocoele or secondary aneurysmal bone cyst.3

Imaging shows expansion of the bone with thinning of the overlying cortex. A ‘ground-glass’ appearance is common on CT. The disease usually affects multiple orbital bones, extending across suture lines.

The main differential diagnosis is hyperostotic meningioma, which occurs in an older age group, and is differentiated on imaging by the presence of a soft tissue component.

Histopathology shows a loose, moderately cellular fibrous stroma containing spicules of woven bone often with characteristic ‘C’ or ‘Chinese character’ shapes. Osteoblastic activity is inconspicuous.6

As the natural history of the lesion is usually one of slow progression, a conservative approach to management is recommended, unless functional

deficits develop. Surgical treatment requires a multidisciplinary craniofacial approach, with removal of as much of the affected bone as possible and reconstruction of the resulting defect in a single operation.9

CASE ILLUSTRATION (Figures 13.2A to D)

Ossifying Fibroma

This is a lesion peculiar to craniofacial bones. The mandible is the site of predilection but the orbit (usually the roof) may rarely be involved.6 It usually

presents in the first two decades of life with a very slowly progressive displacement of the globe. Imaging shows a well circumscribed lesion eroding the bone with a sclerotic margin and foci of internal calcification.

Histopathology reveals trabeculae of bone and osteoid lined by osteoblasts in a cellular stroma.6 A ‘psammomatoid’ variant is described, in which ossicles remniscent of psammoma bodies are seen.10 This variant shows more aggressive behavior and has a greater risk of recurrence following incomplete excision.