Ординатура / Офтальмология / Английские материалы / Tumors of the Eye and Ocular Adnexa_Char_2001

On thin-section MRI performed on a 1.5 Tesla unit, the MR pattern of cavernous hemangioma is typical.9,12 The lesions were hypointense compared to brain and contrasted sharply to orbital fat on T1- weighted images and are either isointense or hyperintense on T2–weighted scans (Figure 17–9). Unfortunately, these T1 and T2 patterns are shared by a number of other benign and malignant orbital

tumors (including neurofibroma, neurilemmoma, solitary fibrous tumor, rare metastases, and hemangiopericytomas). In the minority of cases, these tumors were not confined to the intraconal space, and some had both intraconal and extraconal involvement (see Figure 17–2). In one report, using the serial dynamic MRI technique, a cavernous hemangioma feeder vessel was visualized.13 Surgically, the author’s experience is that feeder vessels are usually not seen.

A number of lesions can simulate a cavernous hemangioma. In over 1,000 previous orbital biopsies, approximately 25 patients had tumors that mimicked the clinical or radiologic (CT or MRI)

Figure 17–5. Optic disc changes associated with pressure from a cavernous hemangioma. Often, these alterations can take a few months to dissipate.

Figure 17–7. Axial CT demonstrates a typical cavernous hemangioma, which is a smooth, rounded, discrete homogeneous mass in an intraconal location with sparing of the orbital apex.

B

Figure 17–8. A, Axial CT scan of bilateral cavernous hemangiomas. B, MRI (T2-weighted) coronal scan demonstrates bilateral cavernous hemangioma.

pattern of cavernous hemangioma.14–18 The mean age of these patients was 37 years (range 8 months to 90 years). Proptosis was present in all cases; 6 had ≥ 6 mm of proptosis. Several were intraconal, some were extraconal, and a minority involved both compartments. As shown in Figures 17–10 to 17–18, lesions other than cavernous hemangioma can simulate the rounded homogenous mass on CT, ultrasonography, or MRI. In 5 of these cases, the history and clinical presentation was sufficient to rule out a cavernous hemangioma. Patients with an arteriovenous malformation or venous varix had proptosis which changed with the Valsalva maneuver; this is not a feature of cavernous hemangioma.19,20 The patients with congenital inclusion cyst (see Figure

A

B

Figure 17–9. A, MRI scan demonstrates anatomic pattern of typical cavernous hemangioma. On T1-weighted image the tumor is hypointense with respect to brain. B, T2- weighted MRI scan demonstrates that the lesion in Figure 17–9A is either isointense or hyperintense with respect to the brain.

C

Figure 17–13. A, Clinical photograph demonstrates axial proptosis in a patient with traumatic conjunctival inclusion cyst. B, Axial CT scan of traumatic conjunctival inclusion cyst. C, Parasagittal reformation of the scan.

larly, a liposarcoma can simulate hemangioma on ultrasonography, but this confusion is not likely on CT or MRI.28–30 Sometimes, cavernous hemangiomas can simulate other tumors. The patient shown in Fig- ure 17–20 was followed up elsewhere for years with a presumed optic nerve tumor. While on axial scan this tumor appeared to involve the optic nerve, on direct coronal T1-weighted scan the tumor can be seen to be inferior to the nerve (see Figures 17–20A to C). It was resected with some visual return. Figure 17–20D and E shows a tumor that was an extradural meningioma that produced a similar imaging pattern.

A varix can sometimes also simulate a cavernous hemangioma, and it has been one of the few lesions

that we have found for which CT is a more useful adjuvant than MRI for diagnosis. On MR scan, often the pattern on T1- and T2–weighted scans show a heterogeneous pattern consistent with hemorrhage (Figure 17–21). The ability to perform a Valsalva maneu-

Figure 17–15. Axial T1-weighted MRI of a benign fibrous histiocytoma.

Figure 17–16. Parasagittal reformatted CT scan demonstrating neurilemmoma.

ver with greater ease, given the relative rapidity of helical CT versus MRI scans, is useful in these cases. Figures 17–22A and B show a case of an orbital varix, referred as a unilateral intraconal tumor, that was shown on CT with Valsalva to be a bilateral orbital varix.28 Usually, these varices will spontaneously present with proptosis, pain, and diplopia; some will spontaneously close and we have had to either embolize or surgically clip the others.31–36 Alternatively, Rootman and colleagues have advocated the use of cyanoacrylate glue intraoperative venography to control outflow and thrombose the lesion so that it can be more easily removed.37 A more extensive orbital varix which required surgical intervention is shown in Figures 17–23A and B.

Rarely, cavernous hemangiomas can produce intracranial involvement. The patient shown in Figures 17–24A and B had such a lesion, with no vision. Orbital hemangiomas have rarely been reported in association with other diseases including the blue rubber nevus syndrome.38

Figure 17–18. Axial CT of biopsy-proven benign fibrous histiocytoma.

The management of cavernous hemangiomas of the orbit is usually straightforward. If a lesion is not causing symptoms and is noted either serendipitously or, as in our bilateral case, as a small, second tumor, no treatment is indicated (Figure 17–25). There is an extremely small likelihood that a rounded, encapsulated, intraconal lesion could be a malignant hemangiopericytoma. Larger tumors can be removed through a number of different approaches, although most commonly, the size and position of these lesions require lateral orbitotomy.39,40 The appearance of a cavernous hemangioma at surgery is quite characteristic (Figure 17–26). The lesion is a discrete, reddish,

encapsulated, molded mass without feeder vessels. Fortunately, as our series documents, with newer surgical techniques, most cavernous hemangiomas can be safely removed without loss of vision.41 This represents an improvement, compared with historic results in which as many as 25 percent of patients had diminished acuity after surgery.6,7 Occasionally, a cavernous hemangioma can be removed through a conjunctival incision.40 In our experience, this is a good approach for an inferior, extraconal lesion (Figure 17–27). As described by Henderson and colleagues, Wright, and others, the effect of partial resec-

tion of this neoplasm is unclear, but most do not recur in that setting.7,41

In small apical cavernous hemangiomas which are symptomatic, a number of approaches have been used to reach this area with less morbidity than a lateral orbitotomy.42–46 At the very apex of the orbit, if the lesion is superior, we have reached it through a combined neurosurgical approach. If the lesion is quite small, symptomatic, and inferior to the nerve, we have often gone through the sinuses. In some of the latter cases, we have actually not removed the tumor but merely opened up the medial inferior wall

Figure 17–22. A, CT scan shows a unilateral orbital mass. B, CT scan with Valsalva maneuver demonstrates enlargement of the varix, with bilateral involvement in the same case.

Figure 17–23. A, Orbital varix with a significant hemorrhage that required intraoperative intervention. Orbital venous varix on a T1- weighted axial scan.The same lesion shown on T2 -weighted axial scan.

B

Figure 17–24. A, Axial T1-weighted MRI scan of a massive cavernous hemangioma. B, Lesion shown in Figure 17–24A on T1-weighted parasagittal scan.

Unfortunately, a neurilemmoma or extradural meningioma can almost perfectly simulate a cavernous hemangioma on imaging studies.16,51 A CT scan of a neurilemmoma is shown in Figure 17–16. The MRI appearance in Figure 17–10 led the author preoperatively to believe this was most likely neurilemmoma, on the basis of the configuration of the anterior and posterior margins of the tumor; however, this was perhaps more of a “roundsmenship ploy” than a statement based on definitive data.

Figure 17–25. Axial T1-weighted MRI scan shows a lesion detected when imaging was performed for headache. This mass is unchanged with over 10 years of follow-up.

Figure 17–28 shows a more cystic-appearing neurilemmoma on CT. The treatment of neurilemmomas is surgical excision. Usually, these tumors can be removed in toto. Occasionally, they can be adjacent to the nerve, and careful microdissection is necessary. Less commonly, they involve the superior orbital tissue.50,52 Incomplete excision of a neurilemmoma has a very small but finite chance of producing malignant transformation of the remnant.49,53 In

Figure 17–26. Photograph of a cavernous hemangioma at the time of surgical excision. This tumor has a characteristic appearance as a reddish, encapsulated, usually smooth mass.

348 TUMORS OF THE EYE AND OCULAR ADNEXA

A

times simulate cavernous hemangioma. Similarly, on histologic evaluation, some fibrous histiocytomas have initially been misdiagnosed as vascular tumors.

Fibrous histiocytomas have a tendency to involve the superior and superomedial orbit. Proptosis, a palpable mass, and decreased vision are the most common presenting findings. Generally, benign fibrous histiocytomas are smaller and have a longer disease course than their malignant counterparts. Surgical removal is sufficient for benign lesions; however, 31 percent of lesions have been found to recur, probably because many were initially incompletely excised. These lesions often have indistinct borders without a surgical capsule. Making the correct diagnosis of a recurrent fibrous histocytoma can be difficult. We had biopsied one patient once before because of a suspicious imaging finding for recurrence; that biopsy was negative. The patient was asymptomatic

B

Figure 17–27. A, Extraconal, inferior-lateral cavernous hemangioma on T1-weighted axial scan. The lesion was removed through a conjunctival incision. B, Lesion shown on a T2-weighted coronal scan.

one case, an orbital neurilemmoma was the presenting finding of neurofibromatosis, type 1 (NF1).52

FIBROUS HISTIOCYTOMA

Fibrous histiocytomas of the orbit are not rare; Font and Hidayat reported on 150 cases from the Armed Forces Institute of Pathology.54 Orbital involvement by this neoplasm was not recognized until the early 1960s. A number of terms have been used to describe benign and malignant forms of this process, including sclerosing hemangioma, dermatofibrosarcoma, and giant cell tumor.55,56

Usually, patients with fibrous histiocytomas present in middle age, although the reported age range is 4 to 85 years. These lesions can be difficult to diagnose, and a number of cases have been misdiagnosed as hemangiomas. Both benign (see Figures 17–14 and 15) and malignant fibrous histiocytomas have CT and MRI characteristics that may some-

A

B

Figures 17–28. A and B, Cystic neurilemmoma on axial (A) and coronal (B) CT scans.

but had the MRI pattern shown in Figure 17–29. A positron emission tomography (PET) scan was felt to be diagnostic for recurrence (Figure 17–30), and the recurrent tumor was removed in an open biopsy.

The role of radiation treatment for fibrous histiocytoma is difficult to determine since no large series has been reported. In the clinicopathologic series reported by Font and Hidayat, in 13 of 18 irradiated cases, the tumor recurred; however, the radiation parameters in these cases were not well defined.54

Some of these tumors are initially benign but recur and undergo malignant degeneration. The patient shown in Figure 17–14 initially had three surgical resections for a recurrent benign tumor and eventually required exenteration after recurrence of

a malignant transformation from the benign fibrous histiocytoma, despite surgery and irradiation. Figure 17–31 shows another patient with malignant histiocytoma with widespread disease who died within 3 months. Of 14 patients with orbital malignant fibrous histiocytoma in the series of Font and Hidayat, 6 died from either local extension or metastases. Exenteration is the treatment of choice.54,57,58

Solitary Fibrous Tumor

Among a group of tumors that had previously been characterized under the ruberic of fibrous histiocytomas are solitary fibrous tumors.59 There have been approximately 10 cases involving the orbit. Figure