Ординатура / Офтальмология / Учебные материалы / Vitreo-retinal Surgery Springer

8.2.2 Angiography

Fluorescein angiography is not particularly helpful in distinguishing between the various choroidal tumors, being most useful for recording secondary changes, particularly after radiotherapy and other conservative therapy. Indocyanine green angiography is better at demonstrating the extent of a choroidal tumor and can provide some diagnostic clues, such as dye wash-out in choroidal hemangiomas.

veal extraocular tumor extension. B-scan ultrasonography can demonstrate a mushroom shape, which is almost pathognomonic of melanoma. The internal acoustic reflectivity, best demonstrated by standardized A-scan echography, is helpful in diagnosis. For example, it tends to be absent with retinal pigment epithelial detachment, low with uveal melanoma, moderate with metastasis, and high with hemangioma.

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■Trans-conjunctival, sutureless, 25-gauge biopsy of posterior segment tumors is performed using three ports, for infusion, illumination, and the vitrector.

■Retinopexy and gas tamponade are not required.

■Anterior segment biopsy is performed through a clear cornea.

With malignant neoplasms, there is a risk of seeding viable tumor cells to other parts of the eye and to the sclerotomy sites. With metastases to the eye, this should not be a problem, because the whole eye is irradiated in such cases. With melanoma, however, seeding may cause recurrences both within the eye and extraocularly. Experience with FNAB suggests that these risks

therapy should be performed before the biopsy.

8.8 Results and Complications

8.8.1 Adequacy of Sample

In most patients, the sample size is much greater than that previously obtained with FNAB [16]. The larger specimen facilitates immunohistochemistry using multiple antibodies (Fig. 8.4) and there is usually sufficient tissue for cytogenetic studies to be undertaken (Fig. 8.5). An inadequate sample occasionally occurs, mostly if the procedure is deliberately curtailed because the tumor is small and located close to the fovea. The larger yield provided by the 25-gauge system compared with FNAB and the ability to see tumor fragments in a gallipot held under the operating microscope have reduced the need for a pathologist to be present in the operating theater at the time of the biopsy.

8.8.2 Sampling Error

When biopsy is performed to grade a melanoma, there is a possibility that the tumor is heterogeneous, in which case the lack of adverse histological or cytogenetic findings might be the result of a sampling error. The chances of such an error occurring would be reduced by taking biopsies from several different sites; if the tumor is large; however, this may increase the risk of complications.

the 25-gauge vitrectomy system, the cannulae should further diminish any possibility of seeding to the sclerotomy sites, when choroidal tumors are biopsied. With iris tumors, there is perhaps a greater theoretical risk of spreading tumor to iris and trabecular meshwork, which, unlike the choroid and ciliary body, are not covered by neural tissue. However, most iris melanomas are low-grade and therefore unlikely to seed readily whereas the minority of iris melanomas that are aggressive have probably already spread diffusely and seeded around the anterior chamber by the time the patient f irst presents.

8.8.4 Hemorrhage

Hemorrhage is the most common complication of tumor biopsy performed with the 25gauge vitreous cutter. Usually the hemorrhage is mild and resolves spontaneously after a few days (Fig. 8.4n). Subretinal hemorrhage can occur and in one of our patients involved the fovea (Fig. 8.5c). Our impression is that hemorrhage is more severe when the tumor is small, possibly because damage to normal choroidal vessels is more likely in such cases. It is also possible that in some patients hemorrhage is induced or aggravated by postoperative hypotony, which can occur in a minority of patients as a result of f luid leakage through the unsutured sclerotomy.

T he reasons why, in combined procedures, biopsy is performed after insertion of a radioactive plaque or tantalum markers, and not before, are (1) so that any immediate hemorrhage caused by the biopsy will not complicate the plaque or marker insertion, by hindering tumor localiza-

tion and (2) so that ocular hypotony and hemorrhage will not be caused by the surgical manipulations required for the implant insertion.

8.9Indications

and Contraindications

8.9.1 Indications

8.8.5Rhegmatogenous Retinal Detachment

We have not seen rhegmatogenous retinal detachment in any of our patients, despite omitting retinopexy and internal tamponade (although one of our patients was treated surgically for retinal detachment by the referring ophthalmologist despite our reassurance that this was exudative and not rhegmatogenous). Our encouraging experience is similar to that of trans-retinal FNAB, which is generally performed without laser treatment or intraocular gas injection. Our impression is that the tumor itself and any associated exudation tamponade the retinotomy.

8.8.6 Other Complications

Other potential complications are the same as for other vitrectomy procedures using the 25-gauge system and include: iatrogenic retinal breaks; inadvertently touching the lens; endophthalmitis; postoperative ocular hypertension; postoperative hypotony; and intraoperative breakage of the 25gauge vitreous cutter [17].

Summary for the Clinician

■The most frequent complication is hemorrhage, which is usually mild.

■An inadequate specimen can result, especially from small tumors.

8.9.1.1 Diagnosis of Metastasis

In our clinic, the commonest indication for choroidal tumor biopsy is to determine the site of the primary malignancy in a patient with an unequivocal metastasis. This information facilitates subsequent management by an oncologist, for example, by directing investigation to particular organs (Fig. 8.4).

8.9.1.2Differentiation Between Metastasis and Melanoma

Rarely, tumor biopsy is indicated to confirm a clinical diagnosis of melanoma or metastasis. For example, a patient with a lightly pigmented tumor has a past history of malignancy, casting doubt on the likely diagnosis of amelanotic melanoma. Some indistinct amelanotic tumors have features consistent with both melanoma and metastasis, making histological studies a necessity (Fig. 8.6)

8.9.1.3Differentiation Between Nevus and Melanoma

Melanocytic tumors of indeterminate malignancy are not unusual in a specialist ocular oncology service such as ours (Fig. 8.5). The standard practice is to observe such lesions until growth is documented by photography, ultrasonography, or both [18]. Such delayed treatment can be considered safe only if it is assumed that uveal melanomas start to metastasize after they have grown large. There is growing circumstantial evidence, based on estimated tumor doubling times, that metastatic spread begins early, several years before treatment, and when tumors are very small, possibly less than 2 mm in diameter [19, 20]. According to this hypothesis, it is the small melanomas that should be treated most urgently because it is with these tumors that any opportunities for

preventing metastatic spread are greatest. Biopsy, therefore, seems a reasonable alternative to prolonged observation in such cases [6]. Unfortunately, these are the tumors that are most difficult to sample, whatever technique is used.

8.9.1.4Confirmation of Local Recurrence of Melanoma after Conservative Treatment

After radiotherapy, tumor enlargement does not necessarily indicate malignant growth. The first author has performed endo-resection on a few patients whose enlarging tumor after radiotherapy proved to consist of macrophages (Fig. 8.7). In such cases, there would be scope for performing a biopsy if enucleation is being considered.

8.9.1.5Confirmation of Intraocular Lymphoma

In view of the rarity of intraocular lymphomas, it is conventional to confirm the diagnosis by means of biopsy (Fig. 8.8). This is especially the case with suspected uveal lymphocytic proliferations (Fig. 8.9).

8.9.1.6 Prognosis

Choroidal and ciliary melanomas tend to develop partial or complete loss of chromosome 3 (i.e., monosomy 3) [21, 22]. In addition, they tend to show gains of the long arm of chromosome 8 [21, 22]. They also develop gains in the short arm of chromosome 6 [23]. Monosomy 3 is associated with a reduction in the actuarial 5-year survival probability from over 90% to less than 50% [24, 25]. Chromosome 8 gains are also associated with an adverse prognosis. Conversely, gains in chromosome 6p indicate a very good chance of survival [23]. It has been suggested that monosomy 3 and disomy 3 melanomas represent two separate classes of melanoma, which are totally distinct from their initiation [26]. We and others have found uveal melanomas containing both monosomy 3 and disomy 3 melanoma cells, which suggests that low-grade, disomy 3 melanomas transform into the high-grade monosomy 3 variety. About 30% of small melanomas (i.e., about 10 mm in diameter) are of the high-grade variety compared with about 50% of large tumors [25]. It is uncertain whether transformation from low-grade to high-grade occurs in large tumors, if treatment is delayed, or whether large tumor size is merely an indicator of increased malignancy, with high-grade tumors tending to be larger at the time of treatment because they grow more rapidly. In any case, cytogenetics seems to be superior to largest basal tumor diameter, tumor