Ординатура / Офтальмология / Английские материалы / Applied Pathology for Ophthalmic Microsurgeons_Naumann, Holbach, Kruse_2008

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VR

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Demarcation line

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Fig. 5.6.26. Retinopathy of prematurity: schematic drawing of the stages: stage 1: demarcation line (a); stage 2: ridge (b); stage 3: ridge with preretinal fibrovascular proliferation (c, d); stage 4: peripheral tractional detachment with attached fovea (e), with foveal detachment (f); stage 5: total retinal detachment (g)

Fig. 5.6.27. International Classification for Retinopathy of prematurity (ICROP) emphasizing location and extent

rization. Traction from epiretinal membranes may lead to secondary retinoschisis (Faulborn et al. 2000). The retinal vessels may be hyalinized later and lipid-laden macrophages may cumulate intravasally. With progressing disease, preretinal neovascularization occurs both at the optic disc and in the midperiphery. When the vitreous detaches, small bridges of neovascularization between the retina and posterior vitreous may tear and cause bleeding either into the vitreous gel or between the vitreous base and the ILM of the retina (subhyaloidal hemorrhage).

5.6.7.2.5

Radiation Retinopathy

Radiation retinopathy appears about 3 years after irradiation, and is basically an ischemic retinopathy in reaction to damage of the endothelium of the retinal arterial bed. Ionizing radiation is used for treatment of choroidal malignant melanomas and orbital and periorbital malignant disease, e.g., in the epipharynx. As the lifespan of capillary endothelial cells in the retina is about 3 years, the failure of endothelial cells to replicate after irradiation peaks in cumulative damage in the capillary bed after 3 years. Occasionally capillaries are filled by glial cells (Archer et al. 1993). However, as early as 1 year after irradiation, hemorrhages, microinfarcts and exudates may be present. In response to the focal closure of the capillary bed, there is exudation of lipid-rich plasma into the retina and the subretinal space.

5.6.2.7.6 Eales’ Disease

Eales disease is an idiopathic obliterative vasculopathy that usually involves the peripheral retina of young adults. Clinically avascular areas in the retina periphery are seen, followed posteriorly by microaneurysms,

dilatation of capillary channels, tortuosity of neighboring vessels, and spontaneous chorioretinal scars. Vascular sheathing with adjacent nerve fiber layer hemorrhages is seen in most patients. The sheathing can manifest as thin white lines, limiting the blood column on both sides of the sheathed vessel to heavy exudative sheathing that can cause vascular occlusion. Although believed to affect primarily the retinal veins, others have reported the same prevalence of both venules and arterioles. Areas of vascular sheathing often leak dye on fluorescein angiography. Neovascularization of the disc (NVD) or neovascularization elsewhere (NVE) in the retina is observed in up to 80 % of patients with Eales disease. The NVE usually is located peripherally, at the junction of the perfused and non-perfused retina. The neovascularization often is the source of vitreous hemorrhage in these eyes, compromising vision. Rubeosis iridis or neovascularization of the iris can develop and may lead to neovascular glaucoma. Fibrovascular proliferation on the surface of the retina may accompany retinal neovascularization. These eyes have associated anteroposterior vitreal traction that could lead to retinal detachment. Cystoid macular edema with significant vision loss can occur in patients with Eales disease due to increased capillary permeability.

The histological appearance of Eales disease is that of an occlusive vasculopathy. Eales disease is believed to be a primary, non-inflammatory disorder of the walls of peripheral retinal vessels, namely the shunt vessels. This often leads to vascular occlusions, peripheral neovascularization, and vitreous hemorrhage. The microvascular abnormalities are seen at the junction of the perfused and non-perfused zones of the retina. Associations with tuberculosis and multiple sclerosis have been suggested, but have not been substantiated in other studies. It is possible that the association of Eales disease with both ocular inflammation and sensitivity to tuberculin protein suggests that this disease may be associated with immunologic phenomena whose mechanisms remain unknown (Gieser 1994; Spitznas 1975). The frequency varies by geography; it is common, e.g., in India (Nagpal 1994). Eales disease is a diagnosis of exclusion, as many other retinal disorders can mimic Eales disease, especially conditions of retinal inflammation or neovascularization.

5.6.2.7.7 Norrie’s Disease

Norrie’s disease is a rare X-linked inherited disease associated with preretinal neovascularization leading to tractional detachment (Warburg 1965; Anderson 1961). The characteristic feature is congenital bilateral blindness with a prominent intraocular mass (pseudoglioma). Noteworthy is a partial avascularity of the retina. The clinical observation that there is a lack of the in-

ner retina and retinal vasculature, which results in retinal hypoxia, led to comparisons with juvenile retinoschisis. However, vice versa, an association between the retinoschisis phenotype and Norrie’s disease was not found (Shastry et al. 2000).

In the end stage of the disease, the retina has lost its normal architecture and is severely gliotic with cysts and extensive compact lamellar bone formation (Michaelides 2004). During development there is a delayed maturation of the neuroretina in Norrie’s disease. Besides changes of the neuroretina, several mouse models have demonstrated primary alterations of the retinal vasculature: Norrie’s disease (Ndp(y/–)) mutant mice that are deficient in norrin develop blindness, and show a distinct failure of retinal angiogenesis (Richter 1998; Rehm 2002). The retinal vasculature is abnormal by postnatal day 9, with abnormal vessels in the inner retina and few vessels in the outer retina (Richter 1998). However, there are increased numbers of blood vessels in the interface of the ganglion cell layer and the nerve fiber layer and a decrease in the inner and outer plexiform layers in Norrie’s disease mice older than 9 days compared with control mice in addition to the previously described alterations of the neuronal retina (Ohlmann 2004, 2005).

Mutations in the Norrie’s disease gene (NDP) have been reported in several retinal disorders which are characterized by vascular abnormalities, including Coats’ disease, Stage 5 ROP, and X-linked FEVR, suggesting that the protein product of NDP, Norrin, may be involved in normal retinal angiogenesis. The association of ND with peripheral venous insufficiency seen in the family reported here and in a Costa Rican pedigree (Rehm 1997) suggest that Norrin may also play a role in extraocular angiogenesis.

5.6.2.7.8 Coats’ Disease

Coats’ disease leads to exudative retinal detachment in children, predominantly in boys. The disease is usually unilateral and presents as a sectorial abnormality of the retinal vasculature (Shields et al. 2001). Massive secondary exudation leads to retinal detachment, which in excessive cases may resemble exophytic retinoblastoma. The sectorial teleangiectasia of the peripheral vessels is considered to be the basic pathology; secondary changes including the leakage of proteinaceous exudates, fibrin and red cells into the retina result in a destruction of the neuronal components of the retina. Macrophagic infiltration accompanies reactionary gliosis and exudation proceeds to intraretinal cyst formation. The subretinal exudate contains myriads of cholesterol crystals, attracting numerous lipidand mela- nin-laden macrophages. Pigmented nodules and subretinal strands derived from the RPE may be present.

Histologically, the teleangiectatic vessels appear to be thin-walled and can be found in addition to arterioles and venules showing mural thickening with possible deposition of PAS-positive material. The accumulation of fat seen as cholesterol clefts and melanin-laden and lipid-laden macrophages in the subretinal space is characteristic of Coats’ disease. The neuronal atrophy in the retina is considered to be secondary to ischemia and retinal detachment. Paradoxically, a significant proliferative retinopathy does not occur, even though neovascular glaucoma may be the cause of enucleation.

5.6.2.7.9

Familial Exudative Vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a bilateral disorder of the peripheral retinal vascular development often associated with vitreous traction (Criswick and Schepens 1969; Gow 1971; see Lang and Maumenee). Systemic associations are absent and no association with prematurity is found. Despite earlier theories that emphasized vitreoretinal changes, it is now clear that the fundamental abnormality in FEVR is the leakiness of the abnormal peripheral retinal vessels (Canny 1976; Laqua 1980).

Histopathology reveals similarities to other peripheral vasculopathies such as Coats’ disease. The vitreous membranes are probably of greatest pathognomic relevance for FEVR. Histopathological characteristics of FEVR include a thickened retina containing dilated, teleangiectatic blood vessels. The peripheral vessel walls are thickened and may demonstrate a perivascular infiltrate (Boldrey 1985). Both intraretinal (Boldrey 1985) and subretinal (Nicholson 1984) inflammation may be present. Cellular and acellular vitreous membranes originating from posterior to the ora serrata may attach to the ILM and throw the retina into folds (Brockhurst 1981). Nevertheless retinal dysplasia has not been described.

The failure to vascularize the peripheral retina is the unifying feature seen in all affected individuals, but, by itself, usually causes no clinical symptoms. The visual problems in FEVR result from secondary complications due to the development of hyperpermeable blood vessels, neovascularization, and vitreoretinal traction. Partial or total retinal detachment occurs in 20 % of cases (van Nouhuys 1982, 1989, 1991).

Fibrous proliferation may be the result of chronic peripheral vascular leakage (De Juan 1985). In contrast to this theory, a “regrowth” of onion skin-like vitreous veils can be observed even after full treatment and regression of peripheral neovascularization. Macular traction or retinal detachment occurs with contraction of mesenchymal elements at the avascular border or of the fibrovascular mass that may occur just anterior to it. Mostly traction is located in the temporal periphery, the area with the most apparent ischemia.

5.6.2.8

Choroidal Neovascularization (Figs. 5.6.28 – 5.6.32)

Age related macular degeneration (AMD) is clinically seen as an atrophic or exudative process (Sarks et al. 1976; Ryan 1987; Sarks et al. 1988; Schatz et al. 1989; Bressler et al. 1988). Macular pathology evolves fairly symmetrically in both eyes, causing loss of central visual acuity at first in one eye, and soon also in the second eye (Strahlman et al. 1983). The periphery of the retina and the choroid usually remains clinically unaffected; however, peripheral AMD (Delaney et al. 1988) or parapapillary choroidal neovascularization (CNV) is relevant in the differential diagnosis of malignomas.

In “dry AMD,” the common denominator histologically is atrophy of the inner and outer segment of the photoreceptors and depletion of the outer nuclear layer to a point where this is replacement by glial cells. A variety of changes may be found in the RPE, which may be hypertrophic, hyperplastic, atrophic or completely absent with fusion of the gliotic outer retina with Bruch’s membrane (Fig. 5.6.28).

Several types of deposit can be found by light microscopy between the RPE and Bruch’s membrane (Abdelsalam et al. 1999; Spraul et al. 1999). “Hard drusen” are well circumscribed, in contrast to the granular and vesicular composition with less distinct borders of “soft drusen” (Sarks et al. 1994). Soft confluent drusen have been described as “basal linear deposits” (Green and

Ender 1993). In contrast, the term “basement membrane deposit” describes deposits found between the cell membrane and the basement membrane (Loeffler and Lee 1998). Each of the deposits on Bruch’s membrane has been the subject of intense speculation in terms of their significance in attracting macrophages, endothelial cells and pericytes, which are the basis of the vasoproliferation in AMD.

According to the current hypothesis, deposits beneath the RPE and in Bruch’s membrane stimulate macrophagic migration into the subpigment epithelial space. These cells release VEGF, which induces endothelial cells of the choriocapillaris to penetrate Bruch’s membrane. The term choroidal neovascularization refers to fibrovascular proliferation, initially between Bruch’s membrane and the RPE, and, subsequently, between the RPE and the photoreceptor layer – but never into the choroid itself. Clinically membranes can best be distinguished by fluorescein and ICG angiography. The TAP and VIP studies have identified clear criteria based on fluorescein angiographic features (Barbazetto et al. 2003) (Fig. 5.6.29a, b).

Specimens of surgically excised CNV membranes were available for histopathological confirmation of the clinical grading (Grossniklaus et al. 1998; Lafaut et al. 2000). It is possible to identify fragments of Bruch’s membrane, the choriocapillaris or of the deeper choroid in these samples. Depending on the presence and location of photoreceptor outer segments, neovascular

292 5.6 Retina and Vitreous

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Fig. 5.6.30. Fibrous hemorrhagic disciform macular degeneration: process confined between Bruch’s membrane (BM) and sensory retina (SR). Inner structures of sensory retina recognizable. Outer layers and receptors at the height of the process missing. Cystoid degeneration in outer layers (CY)

a Hematoxylin-eosin stain shows blood and vascularized connective tissue with variable pigmentation.

b Collagen blue (Masson stain). c In front of the fibrous plaque a new basement membrane (NBM) is formed by proliferating retinal pigment epithelium (arrows)

channels and Bruch’s membrane, classic membranes can be distinguished from occult membranes. Specific features to look for within the fibrovascular membranes are lymphocytes, macrophages and fibroblasts derived from metaplastic RPE (Gass 1994; Nasir et al. 1997).

Advanced processes may be dominated by fibrosis. The fibrotic tissue may be pigmented as a conse-

quence of reactive proliferation of RPE cells, lipofuscin and deposition of the breakdown products of blood, free and within macrophages. A close mechanical connection between CNV or fibrosis and the retina can result in inevitable difficulties for surgical approaches when extraction of the membrane becomes traumatic to the overlying retinal tissue (Fig. 5.6.30).

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Fig. 5.6.30. g Melanin pigmentation from proliferating pigment epithelium (Fontana stain: black). Pigmentation results from RPE-prolif- eration and Hemosiderin plus lipofuscin. h Hemosiderin laden macrophages (HM), Prussian-blue stained

Fig. 5.6.31. Growth pattern of malignant melanoma of the uvea. a Choroidal. b Choroidal with perforation of Bruch’s membrane. c Diffuse growth pattern with extrascleral extension, with collateral detachment (see Chapter 4)

5.6.2.9

Tumors of Choroid and Retina

Both benign and malignant uveal tumors arise most commonly from melanocytes in the uveal tract. Choroidal malignant melanoma is the most frequently encountered malignant intraocular tumor in the routine laboratory (Fig. 5.6.31). Included in the differential diagnosis

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are lymphoid and metastatic neoplasms masquarading as a typical uveitis.

Lymphoid neoplasms may occur in both the retina and the uveal tract (Fig. 5.6.32). Those occurring in the retina are very aggressive, may masquerade as a “retinal vasculitis” or as vitritis (Brown et al. 1995), and need to be differentiated from e.g. DD sarcoidosis (Fig. 5.6.33). They are often associated with cerebral manifestation. Those lymphomas of the uvea are considerably rarer.

Vascular tumors of the retina and choroid may be associated with malformation in the central nervous system (von Hippel-Lindau) and skin (Sturge-Weber).

Very rarely seen are tumors of the RPE, or those derived from glial cells (astrocytomas).

Retinoblastoma, a malignant tumor of the retina, is almost exclusively seen in childhood and arises from retinoblasts. Its difficult diagnosis within a group of entities, which can mimic neoplasms, emphasizes the importance of this tumor (Fig. 5.6.34).

Below, the histological findings of each of the abovementioned tumors will be briefly discussed.

Choroidal malignant melanoma is associated with leakage of proteinaceous fluid beneath the photoreceptors as they interfere with the function of the choriocapillaris and the fluid pumping capacity of the RPE.

In order to define treatment modalities, it is important to accurately measure the size of the tumor in three dimensions. A mushroom shape of the tumor can occur when the tumor penetrates beyond Bruch’s membrane leading to a dilatation of tumor vessels (“turnicat effect”). A pitfall for the surgeon and the radiologist is if the peripheral borders of the tumor are not well defined, and if the tumor infiltrates the adjacent sclera to some degree, which occurs in 90 % of serial sections (Donders 1973). Melanoma rarely erodes or penetrates, the retina (Dunn et al. 1988) – with the exception of the Rønne type malignant melanoma free floating tumor cells in the vitreous.

Large tumors can undergo massive spontaneous hemorrhagic necrosis. Widespread endarteritis is the contributory factor for the extensive infarction of all the intraocular tissues.

Similar to transillumination during surgery, a preliminary investigation of the enucleated eye in the

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“black box” is important to choose the most suitable plane of section including disc and pupil. Cutting of the globe should be performed so that the principal histological section will pass through the center of the tumor. Further, the vortex veins should be dissected and excised, and examined for extraocular spread before the eye is opened. Vortex vein spread is more likely to occur if the base of the center of the tumor is located over the internal orifice of the vein, i.e., in the supero-/ inferonasal and temporal quadrants. Similarly, transcleral spread can be found at any (Fig. 5.6.31). The sclera adjacent to the lamina cribrosa of the optic disc is less than half of the thickness elsewhere. Juxtapapillary malignant melanomas are less than 250 µm from the subdural space. Lymphocytic infiltration in the wall of a vortex vein is frequently seen on routine examination, while tumor cells are seen as clumps, partially or totally occluding the lumen or the wall of the vein.

The microscopic evaluation of the tumor distinguishes spindle cell type variants, epithelioid cell types, and mixed forms (McLean et al., 1978, 1983).

Spindle A cells are closely packed and have elongated oval nuclei with a longitudinal fold in the nuclear membrane. Spindle B cells are larger and have a rounder nucleus in which the nucleolus is prominent. Spindle cells are arranged in “fascicles,” resembling the pattern seen in schwannomas, or demonstrate a perivascular fascicular arrangement. Mitotic figures are not usually seen.

Epithelioid cells are larger than spindle cells and the cytoplasmic rim is larger and more eosinophilic. The boundaries of these cells are more distinct and the cells appear to be separated by an intercellular space. There is a higher nuclear pleomorphism associated with epithelioid tumors, and they are associated with a poorer prognosis. These tumors have a higher mitotic count as determined per 10 – 40 high power fields on conventionally stained section. No consensus has been reached regarding which proportion of epithelioid cells qualifies a uveal melanoma as being of mixed and epithelioid type, respectively. Uveal melanoma cells stain usually (but with variability) for the melanocytic immunohistochemical markers, HMB-45, MelanA and S-100P.

Cells of macrophagic type, as identified by antiCD68 staining, are often present within the uveal melanomas, sometimes as multinucleate cells. Balloon cells (degenerate melanoma cells) or lipid-laden macrophages may also be present within a tumor (Khalil 1983; Grossniklaus et al. 1997). Tumor melanin is not regarded as a significant prognostic marker. Tumor melanin is seen as fine light brown pigment granules, and contrasts the coarser and darker secondary melanophagosomes observed in perivenular macrophages. These are activated by tumor cell apoptosis and focal necrosis with melanin release.

In relation to the histological cell type, the 5-year

survival rate for patients with spindle cell melanomas is 80 %, and for those with epithelioid cell melanomas it is 20 % although epithelioid tumors at first appear to be more radiosensitive (Lommatzsch; Jensen et al. 1982). The peak mortality from metastatic disease, which usually involves the liver, occurs within 2 years of diagnosis or the date of enucleation (Jensen et al. 1982; McLean et al. 1982). While the presence of VEGF expression does not correlate with prognosis (Sheidow et al. 2000), a vascular network pattern and a closed loop pattern of the vasculature indicate a worse prognosis (Sakamoto et al. 1996; Folberg et al. 1997; McLean et al. 1997).

Other prognostic factors include indices of cell proliferation, ploidy analysis and the assessment of genetic abnormalities. Monosomy 3 and defined abnormalities of chromosomes 6 and 8, as determined using fluorescence in-situ hybridisaton (FISH), have consistently been associated with metastatic death in choroidal and ciliary body melanoma (Scholes et al., 1999 – 2003; Damato et al., 2007; Sisley et al., 1998; White et al., 1998). The strongest single predictor of prognosis is loss of heterozygosity detected in chromosome 3; because of the possibility of isochromosome, some of these patients falsely appear to be disomic e.g. in FISH analysis. Other molecular biological techniques, including gene expression profiling analysis (Tschentscher et al., 2003; Worley et al., 2007), may be more accurate ways than karyotyping ot differentiate uveal melanoma patients with favorable and adverse prognoses.

In addition to cell type, mitotic count, mean diameter of the ten largest nucleoli (measured e.g. from sil- ver-stained sections), presence of defined extravascular matrix patterns (e.g. closed loops and networks detected with periodic acid-Schiff staining or clinically with confocal angiography), microvascular density (determined from areas of dense vascularization ofter staining with antibodies to vascular endothelial cells), as well as high numbers of tumor-infiltrating lymphocytes and macrophages have been shown to be independent predictors of subsequent survival in more than one study (Mäkitie et al., 1999, 2001). Determinants of cell proliferation, such as Ki67/MIB-1 or proliferating cell nuclear antigen (PCNA; also known as PC10), have been investigated and found to be of value as prognostic indicators (Mooy and de Jong 1996; Seregard et al. 1998).

Tumor recurrence and metastases have been shown to correlate with the distribution of the amount of DNA in a tumor population using ploidy analyses on fixed tissue (Coleman et al. 1993). Others disagree (Elavathil et al. 1995). Several studies have shown that monosomy of chromosome 3 is by far the most important risk factor for metastasis. There are DNA probes available for detecting monosomy 3 in biopsies of tumors (Sisley 1992, 1997; Prescher 1990, 1992, 1996).