The microcirculation of choroidal and ciliary body melanomas

Quantitative Biomarkers Derived from a Novel, Contrast-Free Ultrasound, High-Definition Microvessel Imaging for Differentiating Choroidal Tumors

Angiogenesis has an essential role in the de novo evolution of choroidal melanoma as well as choroidal nevus transformation into melanoma. Differentiating early-stage melanoma from nevus is of high clinical importance; thus, imaging techniques that provide objective information regarding tumor microvasculature structures could aid accurate early detection. Herein, we investigated the feasibility of quantitative high-definition microvessel imaging (qHDMI) for differentiation of choroidal tumors in humans. This new ultrasound-based technique encompasses a series of morphological filtering and vessel enhancement techniques, enabling the visualization of tumor microvessels as small as 150 microns and extracting vessel morphological features as new tumor biomarkers. Distributional differences between the malignant melanomas and benign nevi were tested on 37 patients with choroidal tumors using a non-parametric Wilcoxon rank-sum test, and statistical significance was declared for biomarkers with p-values < 0.05. The ocular oncology diagnosis was choroidal melanoma (malignant) in 21 and choroidal nevus (benign) in 15 patients. The mean thickness of benign and malignant masses was 1.70 ± 0.40 mm and 3.81 ± 2.63 mm, respectively. Six HDMI biomarkers, including number of vessel segments (p = 0.003), number of branch points (p = 0.003), vessel density (p = 0.03), maximum tortuosity (p = 0.001), microvessel fractal dimension (p = 0.002), and maximum diameter (p = 0.003) exhibited significant distributional differences between the two groups. Contrast-free HDMI provided noninvasive imaging and quantification of microvessels of choroidal tumors. The results of this pilot study indicate the potential use of qHDMI as a complementary tool for characterization of small ocular tumors and early detection of choroidal melanoma.

Vascular Lakes in Uveal Melanoma and Their Association With Outcome

Purpose

Prognostic predictors in uveal melanoma (UM) consist of clinical, histomorphologic, and genetic features. Vascular lakes (VLs) are immature blood vessels within UM with unknown significance for metastatic risk.

Methods

A clinically well-phenotyped cohort of 136 hematoxylin and eosin–stained slides of UM enucleation specimens were retrospectively analyzed on scanned whole-slide images. These were annotated for VL in QuPath, assessing VL number and area. Using SPSS (V27.0), the Mann–Whitney U test and Cox regression were applied to evaluate whether there was any correlation between VL number and area within the tumor (VL-TA) compared with other prognostic parameters and patient survival times.

Results

UMs with monosomy 3 (M3) have significant differences in their VL numbers (P = 0.008) and VL-TA ratios (P = 0.002) compared with disomy 3-UM. Nuclear BAP1-negative (nBAP1^–) UMs have significant differences in their VL-TA ratio (P = 0.002) compared to nBAP1⁺ UMs. Survival times of patients with UM with epithelioid-celled tumors varied depending on their VL-TA ratio (P = 0.057). Similarly, in M3-UM, significant differences in survival (P = 0.009) were seen in patients, depending on VL number. Finally, patients with UM with shorter overall survival showed significant differences in their tumor VL-TA ratios (P = 0.043) and the number of VLs present (P = 0.002) than patients with UM who had longer survival.

Conclusions

Our pilot data suggest that VL-TA is an additional poor prognostic parameter in UM.

Translational Relevance

Digital analysis of UM can be easily performed to assess various prognostic parameters. Our pilot study demonstrates that UM-VL could be combined with other parameters to determine metastatic risk of patients with UM.

MR imaging characteristics of uveal melanoma with histopathological validation

Purpose

To evaluate the magnetic resonance imaging (MRI) characteristics of uveal melanoma (UM), to compare them with fundoscopy and ultrasound (US), and to validate them with histopathology.

Methods

MR images from 42 UM were compared with US and fundoscopy, and on 14 enucleated cases with histopathology.

Results

A significant relationship between the signal intensity on T1 and pigmentation on histopathology was found (p=0.024). T1 hyperintense UM were always moderately or strongly pigmented on histopathology, while T1-hypointense UM were either pigmented or non-pigmented. Mean apparent diffusion coefficient (ADC) of the UM was 1.16 ± 0.26 × 10⁻³ mm²/s. Two-thirds of the UM had a wash-out and the remaining a plateau perfusion time-intensity curve (TIC). MRI was limited in evaluating the basal diameter of flat tumors. US tends to show larger tumor prominence (0.5mm larger, p=0.008) and largest basal diameter (1.4mm larger, p<0.001). MRI was good in diagnosing ciliary body involvement, extrascleral extension, and optic nerve invasion, but limited on identifying scleral invasion. An increase of tumor prominence was associated with lower ADC values (p=0.030) and favored a wash-out TIC (p=0.028). An increase of tumor ADC correlated with a plateau TIC (p=0.011).

Conclusions

The anatomical and functional MRI characteristics of UM were comprehensively assessed. Knowing the MRI characteristics of UM is important in order to confirm the diagnosis and to differentiate UM from other intra-ocular lesions and because it has implications for treatment planning. MRI is a good technique to evaluate UM, being only limited in case of flat tumors or on identifying scleral invasion.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00234-021-02825-5.

SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN SMALL CHOROIDAL MELANOMAS AND CHOROIDAL NEVI

PURPOSE

To evaluate the use of swept-source optical coherence tomography angiography to detect distinct vascular features in small choroidal melanomas and choroidal nevi.

METHODS

Patients with a choroidal nevus or a treatment-naïve choroidal melanoma were imaged with color fundus photography, ultrasound, and swept-source optical coherence tomography angiography (12 × 12 mm). High-risk features including overlying fluid, orange pigment, shaggy photoreceptors, acoustic hollowness, depth >2 mm, and basal diameter >5 mm were assessed. Optical coherence tomography angiography vascular markers included: choroidal vessel visualization, choroidal vessel depth, and choriocapillaris flow signal, assessed qualitatively by comparison with surrounding, unaffected choriocapillaris.

RESULTS

Twenty-nine lesions were included in this study, seven flat choroidal nevi, 17 elevated choroidal nevi, and 5 choroidal melanomas. Distinct vascular patterns were noted between flat nevi, elevated nevi, and small choroidal melanomas. Choroidal melanomas displayed two types of vasculature: "nevus-like" vasculature with straight parallel vessels and complex vasculature with vascular loops and crosslinking. Visualized choroidal vessels were significantly deeper in melanomas (110 µm) than elevated (84 µm) or flat nevi (70 µm). In a size-matched subanalysis of 5 elevated choroidal nevi and 5 choroidal melanomas, choroidal melanomas had increased mean choroidal vessel depth (P = 0.015), deepest choroidal vessel visualized (P = 0.034), and presence of a deep choroidal vessel >155 µm (P = 0.048).

CONCLUSION

Swept-source optical coherence tomography angiography may detect distinct vascular features in choroidal nevi and small choroidal melanomas.

Optical coherence tomography angiography (OCTA) applications in ocular oncology

Optical coherence tomography angiography (OCTA) is a revolutionary method in the visualization of the vascular system in different retinal and choroidal layers. During the last 4 years since the commercial availability of different OCTA devices, attempts have been made to utilize this technology in various aspects of ocular oncology from the differentiation of benign and malignant lesions to assisting in evaluation of post-treatment complications, such as radiation retinopathy. However, current OCTA technology is restricted by various artefacts and inherent limitations, some of which are more pronounced in the presence of elevated tumoural lesions. Imminent advancements in OCTA systems and image acquisition processes promise a great potential for application of OCTA in ocular oncology.

Periodic acid-Schiff-positive loops and networks as a prognostic factor in oral mucosal melanoma

The prognostic factors of oral mucosal melanoma (OMM), a rare and aggressive neoplasm, remain to be determined. The aim of this study is to investigate the prognostic significance of vasculogenic mimicry in OMM. The clinical data of 62 patients with primary OMM treated in Shanghai Ninth People's Hospital from April 2007 to April 2012 were retrieved and analyzed retrospectively. Staining of periodic acid-Schiff (PAS) and CD31 immunohistochemistry were performed to evaluate the prognostic value of PAS-positive patterns, blood lakes, and microvascular density. PAS-positive loops and networks (P<0.001) as well as blood lakes (P=0.040) were found to be predictors of overall survival (OS). The presence of PAS-positive loops and networks was an independent prognostic factor of poor OS in multivariate analysis (P=0.002). Although the presence of PAS-positive loops and networks was associated with hematogenous metastasis (P=0.041) and lymphogenous metastasis (P=0.041), it was not an independent predictor of both types of metastasis in multivariate analysis. Microvascular density was not associated with OS (P=0.627) and metastasis of OMM patients. PAS-positive loops and networks have a significant prognostic value in OMM. Detection of PAS-positive patterns may lead to better staging and serve as a prognostic parameter of OMM.

Impact of macrophages on tumor growth characteristics in a murine ocular tumor model

Tumor associated macrophages (TAM), mean vascular density (MVD), PAS positive extravascular matrix patterns, and advanced patients' age are associated with a poor prognosis in uveal melanoma. These correlations may be influenced by M2 macrophages and their cytokine expression pattern. Thus, the effect of TAM and their characteristic cytokines on histologic tumor growth characteristics were studied under the influence of age. Ninety five CX3CR1(+/GFP) mice (young 8-12weeks, old 10-12months) received an intravitreal injection of 1 × 10(5) HCmel12 melanoma cells. Subgroups were either systemically macrophage-depleted by Clodronate liposomes (n = 23) or received melanoma cells, which were pre-incubated with the supernatant of M1- or M2-polarized macrophages (n = 26). Eyes were processed histologically/immunohistochemically (n = 75), or for flow cytometry (n = 20) to analyze tumor size, mean vascular density (MVD), extravascular matrix patterns, extracellular matrix (ECM) and the presence/polarization of TAM. Prognostically significant extravascular matrix patterns (parallels with cross-linkings, loops, networks) were found more frequently in tumors of untreated old compared to tumors of untreated young mice (p = 0.024); as well as in tumors of untreated mice compared to tumors of macrophage-depleted mice (p = 0.014). Independent from age, M2-conditioned tumors showed more TAM (p = 0.001), increased collagen IV levels (p = 0.024) and a higher MVD (p = 0.02) than M1-conditioned tumors. Flow cytometry revealed a larger proportion of M2-macrophages in old than in young mice. The results indicate that TAM and their cytokines appear to be responsible for a more aggressive tumor phenotype. Tumor favoring and pro-angiogenic effects can be directly attributed to a M2-dominated tumor microenvironment rather than to age-dependent factors alone. However, an aged immunoprofile with an increased number of M2-macrophages may provide a tumor-favoring basis. Further, old mice represent a more suitable tumor model instead of young mice since their histologic tumor pattern better resembles human tumors.

Intravitreally Injected HCmel12 Melanoma Cells Serve as a Mouse Model of Tumor Biology of Intraocular Melanoma

PURPOSE

To establish a mouse model with histologic characteristics of uveal melanoma for investigation of intraocular tumor biology of melanoma.

METHODS

After injection of 1 × 10(5) of HCmel12 melanoma cells, a cutaneous melanoma cell line, into the vitreous of CX3CR1(+/GFP) or C57Bl/6 mice (n = 12), tumor growth patterns, clinicopathological features, angiogenesis and metastatic behavior were analyzed by histology (hematoxylin and eosin, periodic acid-Schiff without hematoxylin) and immunohistochemistry (HMB45/MART-1-Ab, F4/80-Ab, green fluorescent protein (GFP)-Ab and VE-cadherin-Ab).

RESULTS

HCmel12 cells formed intraocularly growing tumor masses, which showed histologic features of intraocular melanoma such as angiotropism, intratumoral endothelial-lined vasculature, vasculogenic mimicry including prognostic significant extravascular matrix patterns, and invasion by inflammatory cells, in particular macrophages. There was no difference in tumor growth characteristics between CX3CR1(+/GFP) and C57Bl/6 mice. Five of 10 mice proceeded to extrascleral tumor growth and three of these developed metastases.

CONCLUSIONS

Intraocularly injected HCmel12 cells developed tumor masses with histologic characteristics of aggressive melanoma similar to human uveal melanoma. Since hematogenous dissemination to the liver was not observed, intravitreally injected HCmel12 cells do not qualify as a model for metastasizing intraocular melanoma. However, since the eye represents a semi-closed compartment with access to constant blood supply, these intraocular tumors represent a model for studies of isolated parameters in general tumor biology of intraocular melanoma.

Tumor cells forming sinusoids connected to vasculature are involved in hemorrhage of pineal choriocarcinoma

Intratumor hemorrhage is a poor prognostic factor in pineal choriocarcinoma (PCCC). The aim of this study was to understand the relationship of tumor cells to the blood vessels to gain insights into the formation of intratumor hemorrhage in PCCC. The clinical data indicated that total tumor removal by surgical procedures followed immediately by radiotherapy and chemotherapy improved the prognosis in PCCC. The PCCC tissues removed from the patients were examined by histology and immunohistochemistry. Hematoxylin and eosin staining showed that the tumor stroma mainly consists of hemorrhagic tissues with tumor cells scattered inside. The pattern of distribution suggests that the tumor cells were possibly flushed and compressed by the bleeding. The tumor cells tended to form sinusoids that lacked CD34, but laminin expression provided evidence of vasculogenic mimicry. Interestingly, CD34-positive blood vessels were found connected to these sinusoids, suggesting that blood may flow from the tumor vasculature to the sinusoids. This may subsequently cause the enlargement of the sinusoids, blood clotting, the widening of the blood lakes, and eventually extensive hemorrhagic necrosis. Our study identified the key features of the PCCC vasculature. The findings add to the previous understanding of the formation of vascular channels, blood lakes, and extensive hemorrhagic necrosis. The intimate connections between the tumor-formed sinusoids and the blood vessels might be a major cause of severe hemorrhage in PCCC. The new information may be useful for the development of treatment strategies for managing PCCC.

Clinical, pathologic, and imaging features and biological markers of uveal melanoma

Uveal melanoma has unique clinical and pathologic features including virtually exclusive metastasis to the liver in high-risk cases. In this chapter, the clinical findings in uveal melanoma and diagnostic methods including imaging tests and serum markers are described. Additionally, the histopathologic features including the modified Callender classification and immunohistochemical findings of uveal melanoma are described.

Ocular melanoma

CONTEXT

Intraocular melanoma of the ciliary body and choroid is the most common primary ocular malignant tumor in adults and the most common noncutaneous melanoma.

OBJECTIVE

To describe the most salient clinical features, histopathologic findings, and treatment modalities of intraocular melanoma, as well as the novel therapies currently being tested.

DATA SOURCES

Clinically, it is important to determine which lesions carry a worse prognosis so as to offer patients the best treatment modalities available. Tumor location, size, histopathology, cytogenetic abnormalities, and tumor profiling are all used in determining the risk of death from metastatic disease of uveal melanocytic lesions. Despite successful local tumor control, up to 50% of patients have metastatic disease within 15 years of diagnosis; there is no effective treatment for metastatic disease.

CONCLUSIONS

Pathologists should be aware of the importance of tumor gross description, cellular histopathology classification, the use of fine-needle aspiration biopsy coupled with cytogenetics, and the new classification of uveal malignant melanomas that is based on chromosome 3 status.

Vasculogenic mimicry: a new prognostic sign of gastric adenocarcinoma

Vasculogenic mimicry (VM) has been generally recognized as a new pattern of tumor neovascularization. It presents in many human malignancies. Till now, there is no report about VM in gastric adenocarcinoma (GAC). In this study, we collected 173 paraffin-embedded human GAC samples, with detailed follow-up and clinicopathologic data. CD31/ periodic acid-Schiff (PAS) double staining, immunohistochemical staining of CK8 & 18 and laminin were performed to validate the existence of VM in GAC. Microvascular density (MVD) and vasulogenic mimicry density (VMD) were counted respectively. VM was observed in 40 of the 173 GAC patients, especially in poorly differentiated GAC (P = 0.014). Patients with VM were prone to hematogenous metastasis and distant recurrence compared with patients without VM (P = 0.020, 0.029). Higher VMD values was also associated with hematogenous metastasis (P = 0.003). Immunohistochemical staining index (SI) of hypoxia-inducible factor 1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)-2, and MMP-9 were compared between the VM and non-VM group. The SI of four factors were all higher in the VM group than those of non-VM group (P = 0.000, 0.000, 0.004, 0.009, respectively). The Kaplan-Meier survival analysis showed that the VM group has shorter life span compared with non-VM group (P = 0.022). Cox proportional hazards model indicated that the presence of VM and TNM stage were independent predictors of poor prognosis (P = 0.039 and 0.004) for GAC. In conclusion, VM exists in GAC, especially in poorly differentiated GAC. Additionally, it is an unfavorable prognostic indictor for GAC. Hypoxia may play a role in VM formation in GAC.

Choroidal perfusion in eyes with untreated choroidal melanoma

PURPOSE

Previous studies indicate that ocular blood flow is altered in eyes with choroidal melanoma. In the present study pulsatile ocular blood flow (POBF) was assessed to investigate whether there exists a correlation between tumour size and ocular blood flow parameters.

METHODS

Twenty-two patients with unilateral untreated choroidal melanoma were studied using two measurement techniques: POBF was measured with a pneumotonometer and local foveal fundus pulsation amplitude (FPA) by laser interferometry, and results were correlated. Tumour volume was calculated using the ellipsoidal solid model and was correlated to POBF and FPA.

RESULTS

Levels of POBF and FPAs tended to be higher in tumour eyes compared with unaffected eyes, but the differences did not reach the level of significance. Both methods showed a high degree of correlation in unaffected eyes. In tumour eyes the correlation was slightly less pronounced. There was no correlation between tumour and POBF or FPA.

CONCLUSIONS

Our results do not indicate choroidal hyperperfusion in patients with choroidal melanoma. The clinical usefulness of measuring POBF in tumour patients may be limited.

Comparing vasculogenic mimicry with endothelial cell-lined vessels: techniques for 3D reconstruction and quantitative analysis of tissue components from archival paraffin blocks

We previously described techniques to generate 3-dimensional reconstructions of the tumor microcirculation using immunofluorescence histochemistry and laser scanning confocal microscopy on serial sections from archival formalin-fixed, paraffin-embedded tissues. By aligning sequential z-stacks in an immersive visualization environment (ImmersaDesk), the need to insert fiduciary markers into tissue was eliminated. In this study, we developed methods to stitch overlapping confocal z-series together to extend the surface area of interest well beyond that captured by the confocal microscope objective and developed methods to quantify the distribution of markers of interest in 3 dimensions. These techniques were applied to the problem of comparing the surface area of nonendothelial cell-lined, laminin-rich looping vasculogenic mimicry (VM) patterns that are known to transmit fluid, with the surface area of endothelial cell-lined vessels in metastatic uveal melanoma to the liver in 3 dimensions. After labeling sections with antibodies to CD34 and laminin, the surface area of VM patterns to vessels was calculated by segmenting out structures that labeled with laminin but not with CD34 from those structures labeling with CD34, or CD34 and laminin. In metastatic uveal melanoma tissues featuring colocalization of high microvascular density [66.4 microvessels adjusted for 0.313 mm2 area (range 56.7 to 72.7)] and VM patterning, the surface area of VM patterns was 11.6-fold greater (range 10.8 to 14.1) than the surface provided by CD34-positive vessels. These methods may be extended to visualize and quantify molecular markers in 3 dimensions in a variety of pathologic entities from archival paraffin-embedded tissues.

Malignant melanoma in the 21st century, part 2: staging, prognosis, and treatment

Critical to the clinical management of a patient with malignant melanoma is an understanding of its natural history. As with most malignant disorders, prognosis is highly dependent on the clinical stage (extent of tumor burden) at the time of diagnosis. The patient's clinical stage at diagnosis dictates selection of therapy. We review the state of the art in melanoma staging, prognosis, and therapy. Substantial progress has been made in this regard during the past 2 decades. This progress is primarily reflected in the development of sentinel lymph node biopsies as a means of reducing the morbidity associated with regional lymph node dissection, increased understanding of the role of neoangiogenesis in the natural history of melanoma and its potential as a treatment target, and emergence of innovative multimodal therapeutic strategies, resulting in significant objective response rates in a disease commonly believed to be drug resistant. Although much work remains to be done to improve the survival of patients with melanoma, clinically meaningful results seem within reach.

[Macroscopic and histological data in the prognosis of malignant choroidal melanoma]

The macroscopic study of choroidal melanoma gives information on tumor extension and tumor size, which help in determining the prognosis and in making the therapeutic choice. Numerous microscopic changes observed in melanomas are also important in the prognosis. However, the number of available histologic specimens has dramatically decreased since the generalized use of conservative radiation treatment. Except in cases of enucleation or choroidectomy, the histologic criteria to establish the prognosis are not available in many cases and cannot be used for wide-range statistical studies.

A gene transfer comparative study of HSA-conjugated antiangiogenic factors in a transgenic mouse model of metastatic ocular cancer

Different antiangiogenic and antimetastatic recombinant adenoviruses were tested in a transgenic mouse model of metastatic ocular cancer (TRP1/SV40 Tag transgenic mice), which is a highly aggressive tumor, developed from the pigmented epithelium of the retina. These vectors, encoding amino-terminal fragments of urokinase plasminogen activator (ATF), angiostatin Kringles (K1-3), endostatin (ES) and canstatin (Can) coupled to human serum albumin (HSA) were injected to assess their metastatic and antiangiogenic activities in our model. Compared to AdCO1 control group, AdATF-HSA did not significantly reduce metastatic growth. In contrast, mice treated with AdK1-3-HSA, AdES-HSA and AdCan-HSA displayed significantly smaller metastases (1.19+/-1.19, 0.87+/-1.5, 0.43+/-0.56 vs controls 4.04+/-5.12 mm3). Moreover, a stronger inhibition of metastatic growth was obtained with AdCan-HSA than with AdK1-3-HSA (P=0.04). Median survival was improved by 4 weeks. A close correlation was observed between the effects of these viruses on metastatic growth and their capacity to inhibit tumor angiogenesis. Our study indicates that systemic antiangiogenic factors production by recombinant adenoviruses, particularly Can, might represent an effective way of delaying metastatic growth via inhibition of angiogenesis.

Echographic examination with new generation contrast agent of choroidal malignant melanomas

PURPOSE

To determine the efficacy of echography with new generation contrast agents in visualizing vascularization of choroidal malignant melanomas.

METHODS

An echographic contrast medium consisting of phospholipidic microbubbles filled with sulphur hexafluoride (Sonovue) was used to visualize microcirculation in 25 cases of choroidal lesions already diagnosed with standardized echography (21 choroidal malignant melanomas, four disciform lesions).

RESULTS

In untreated malignant melanomas contrast agent echography revealed the presence of a dense microcirculation inside the mass. In one case vitreal seeding of the contrast agent was detectable before enucleation and histological examination revealed the presence of tumoral cells. In 12 cases treated with transpupillary thermotherapy, contrast agent echographic evaluation showed heavy regression of microcirculation after 1 week, confirmed in one case by histology, and a reduction of 70-80% in dimensions after 6 months (which appeared to have stabilized at subsequent examinations). In four cases treated with proton beam brachytherapy 2 years prior to our examination, contrast agent echography showed the absence of a microvascular network and the presence of large vessels and blood lakes. In four cases of disciform lesion, deep and superficial retina-associated vascularization was observed, with a weak spread of contrast agent inside the lesion.

CONCLUSION

Live representation with good resolution of choroidal malignant melanoma microcirculation was obtained.

Distinguishing fibrovascular septa from vasculogenic mimicry patterns

CONTEXT

Molecular analyses indicate that periodic acid-Schiff (PAS)-positive (laminin-rich) patterns in melanomas are generated by invasive tumor cells by vasculogenic mimicry. Some observers, however, consider these patterns to be fibrovascular septa, generated by a stromal host response.

OBJECTIVE

To delineate differences between vasculogenic mimicry patterns and fibrovascular septa in primary uveal melanomas.

DESIGN

Frequency distributions, associations with outcome, and thicknesses of trichrome-positive and PAS-positive looping patterns were determined in 234 primary uveal melanomas. Sequential sections of 13 additional primary uveal melanomas that contained PAS-positive/trichrome-negative looping patterns were stained for type I and type IV collagens, laminin, and fibronectin. Real-time quantitative polymerase chain reaction was performed on RNA from cultured uveal melanoma cells for the expression of COL1A1, COL4A2, and fibronectin.

RESULTS

Trichrome-positive loops were encountered less frequently than PAS-positive loops (10% vs 56%, respectively). Death from metastatic melanoma was strongly associated with PAS-positive (P < .001) but not with trichrome-positive (P = .57) loops. Trichrome-positive loops were significantly thicker than PAS-positive loops (P < .001). The PAS-positive patterns stained positive for laminin, type I and type IV collagens, and fibronectin. Type I collagen was detected within melanoma cells and focally within some PAS-positive patterns. Real-time quantitative polymerase chain reaction revealed 3-fold, 25-fold, and 97-fold increases, respectively, in expression of COL4A2, fibronectin, and COL1A1 by invasive pattern-forming primary melanoma cells compared with poorly invasive non-pattern-forming cells.

CONCLUSIONS

Fibrovascular septa are rare and prognostically insignificant in uveal melanomas, whereas vasculogenic mimicry patterns are associated with increased mortality. Type I collagen, seen focally in some vasculogenic mimicry patterns, may be synthesized by tumor cells, independent of a host stromal response.

"Melanoma inhibitory activity" (MIA): a promising serological tumour marker in metastatic uveal melanoma

PURPOSE

To assess the role of "melanoma inhibitory activity" (MIA) as a potential serum marker for screening and detection of metastatic uveal melanoma.

DESIGN

Prospective, clinical study.

MATERIAL AND METHODS

Serum samples of 305 patients with uveal melanoma were collected. Serum samples were analysed by a one-step enzyme-linked immunosorbent assay (ELISA) to quantify the MIA serum levels. All patients underwent a standardized echography of the globe to evaluate maximum tumour height and were checked for systemic metastasis of the tumour by liver enzyme tests and ultrasonography of the liver.

RESULTS

Twenty patients (6.6%) had proven metastatic disease; eight of them developed it during follow-up. The mean serum concentration of MIA in the 285 patients without metastasis was 6.72 ng/ml, whereas the mean serum concentration of MIA in the 20 patients with metastasis was 13.03 ng/ml (P<0.001). The eight patients who developed metastatic disease during follow-up showed an MIA of 5.92 ng/ml before detection of metastasis and 12.21 ng/ml afterwards (P<0.001). MIA serum levels did neither correlate with the tumour height or to whether local therapy had been applied.

CONCLUSION

The elevation of MIA serum levels in patients with metastatic disease from melanoma supports its promising role as a serum marker for monitoring patients with uveal melanoma.

Vasculogenic mimicry

The term vasculogenic mimicry describes the formation of fluid-conducting channels by highly invasive and genetically dysregulated tumor cells. Two distinctive types of vasculogenic mimicry have been described. Vasculogenic mimicry of the tubular type may be confused morphologically with endothelial cell-lined blood vessels. Vasculogenic mimicry of the patterned matrix type in no way resembles blood vessels morphologically or topologically. Matrix proteins such as laminin, heparan sulfate proteoglycan, and collagens IV and VI have been identified in these patterns. The patterned matrix anastomoses with blood vessels, and systemically injected tracers co-localize to these patterns. Vasculogenic mimicry of the patterned matrix type has been identified in uveal, cutaneous and mucous membrane melanomas, inflammatory and ductal breast carcinoma, ovarian and prostatic carcinoma, and soft tissue sarcomas, including synovial sarcoma rhabdomyosarcoma, osteosarcoma, and pheochromocytoma. Because the microcirculation of many tumors may be heterogeneous -- including incorporated or co-opted vessels, angiogenic vessels, mosaic vessels, and vasculogenic mimicry of the tubular and patterned matrix types -- therapeutic regimens that target angiogenesis alone may be ineffective against highly invasive tumors that contain patterned matrices. Vasculogenic mimicry provides an opportunity to investigate the interrelationships between the genetically dysregulated invasive tumor cell, the microenvironment, and the malignant switch.

Expression of Vascular Endothelial Growth Factor in Uveal Melanoma Is Independent of 6p21-Region Copy Number

Purpose: Overexpression of vascular endothelial growth factor (VEGF) and overrepresentation of the 6p region have been reported with a wide variation in uveal melanoma. The aim of the current study is to identify the frequency of copy number alteration in the 6p21 region and its correlation with the expression of VEGF in uveal melanoma.

Experimental Design: We studied 88 uveal melanomas for copy number change in the 6p region by comparative genomic hybridization and/or chromogenic in situ hybridization. Expression of VEGF protein was estimated by immunohistochemistry. In 15 tumors, VEGF mRNA expression was also studied by quantitative reverse transcription–PCR (RT-PCR) and VEGF splice variants were detected by RT-PCR.

Results: Copy number of the 6p21 region was successfully estimated in 37 tumors. In 10 (27%) of those, overrepresentation of the 6p21 region was detected. There was no statistically significant difference in VEGF expression between tumors with and without gain of 6p21 (P = 0.82). VEGF expression was not confined to the tumors and was also detected in the surrounding normal tissue. Expression of VEGF, detected by quantitative RT-PCR, was concordant with expression of VEGF protein. Different VEGF isoforms were expressed in different tumors with no obvious correlation with disease status.

Conclusion: VEGF is overexpressed in a significant number of uveal melanomas. It should be noted that VEGF is not a candidate oncogene in uveal melanoma with 6p gain/amplification. VEGF overexpression other than structural amplification is probably significant in the pathogenesis of uveal melanomas, and its mechanism must be sought.

Prognostic factors for survival after enucleation for choroidal and ciliary body melanomas

PURPOSE

To evaluate prognostic factors for the survival of patients treated by enucleation for choroidal and ciliary body melanomas.

METHODS

The study included 293 consecutive patients (147 men and 146 women) treated by enucleation for a choroidal or ciliary body melanoma during the period 1955-2000. The median age at treatment was 61 years (range 26-88 years). Clinical and histopathological findings, vital status at October 1st, 2002, and cause of death were registered. Prognostic factors for survival were evaluated by univariate and multivariate Cox proportional hazards analysis and by Kaplan-Meier survival analysis.

RESULTS

Follow-up was complete. The median follow-up time was 6.2 years (range 21 days to 43.4 years) and the median potential follow-up time was 25.7 years (range 1.9-47.7 years). In multivariate Cox proportional hazards analysis an increased risk of melanoma-related death was found for largest basal diameter (n = 264, p < 0.001, mortality rate ratio (RR) = 1.09 for continuous parameter in mm), anterior tumour margin at the iris/ciliary body versus choroid (p < 0.001, RR = 2.22), and non-spindle cell type versus spindle cell (p = 0.047, RR = 1.45). An increased risk of death from all causes was found for men versus women (n = 266, p = 0.02, RR = 1.41), high age (p < 0.001, RR = 1.41 for continuous parameter in 10-year age groups), largest basal diameter (p < 0.001, RR = 1.07), anterior tumour margin at the iris/ciliary body (p = 0.02, RR = 1.52), and non-spindle cell type (p = 0.04, RR = 1.34).

CONCLUSION

The risk of melanoma-related death after enucleation for a choroidal or ciliary body melanoma was high for tumours with large basal diameter, of non-spindle cell type and anterior location. Additional risk factors for death from all causes were male sex and high age.

Microvascular loops and networks in uveal melanoma

Microvascular patterns--three-dimensional architectural arrangements of microvessels and extravascular matrix in uveal melanoma--were discovered when investigators were looking for histopathological features of sufficient size to be imaged clinically. Evidence that these patterns may be formed by tumour cells and that they may be able to conduct plasma and blood as well as discovery of similar elements in other cancers make them of general importance. Of nine different patterns described, closed microvascular loops and networks have been studied most extensively. When cell type, microvascular density and nucleolar size are controlled for, these two patterns independently predict time to metastasis. In addition to visualization in tumour specimens stained with periodic acid-Schiff reagent, they can often be visualized clinically on confocal indocyanine green angiography. The presence of networks is clinically associated with probability of growth of small uveal melanocytic tumours and with the rate of regression of uveal melanoma after brachytherapy. Networks are also associated with development of exudative retinal detachment from uveal melanoma. Histopathological studies show that loops and networks are less common in tumours enucleated after irradiation and that they are frequently repeated in metastases of uveal melanoma. Avenues for immediate future research include detailed elucidation of the histogenesis of microvascular patterns and determination of these patterns in metastatic melanoma to identify new histopathological characteristics for prognostication when clinical metastases have developed.

Ocular melanoma

This article reviews the current pathogenesis, molecular changes, diagnosis, and treatment of ocular melanomas. Ocular melanomas can involve the eyelid, conjunctiva, intraocular structures, and the orbit. The most common eye melanoma involves the uveal tract and is responsible for approximately 13% of melanoma deaths. Uveal melanomas account for 10% of all melanomas.

Complex microcirculation patterns detected by confocal indocyanine green angiography predict time to growth of small choroidal melanocytic tumors: MuSIC Report II

PURPOSE

Multiple independent laboratories have confirmed the histologic observation that some tumor microcirculation patterns (MCPs) in uveal melanomas are associated strongly with death resulting from metastatic disease. Because these patterns are imageable with confocal indocyanine green angiography (ICG), we designed a prospective study to evaluate whether these angiographically detectable MCPs predict time to tumor growth.

DESIGN

Observational case series, prospective, non-randomized.

PARTICIPANTS

Ninety-eight patients with unilateral, small, choroidal melanocytic tumors.

METHODS

The following information and tumor characteristics were recorded for each patient: demographic parameters, best-corrected visual acuity, intraocular pressure, related visual symptoms, location and dimension of tumor, pigmentation, orange pigment, drusen, tumor-associated hemorrhage, subretinal fluid, and confocal ICG angiographically determined microcirculation patterns-silent (avascularity), normal (preexisting normal choroidal vessels within the tumor), straight vessels, parallel without and with cross-linking, arcs without and with branching, loops, and networks.

MAIN OUTCOME MEASURES

Time to growth of the tumor, with growth defined as an increase in the maximal apical tumor height of 0.5 mm measured by standardized A-scan ultrasonography, photographic documentation of an increase of the largest basal diameter of at least 1.5 mm, advancement of one tumor border of at least 0.75 mm, or a combination thereof.

RESULTS

Twenty-eight of the 98 tumors in this study (29%) met the predetermined criteria for tumor growth. The median time to growth was 127 days (range, 51-625 days). The following tumor characteristics were significantly associated with time to tumor growth: flashes (P = 0.0224), orange pigment (P = 0.012), subretinal fluid (P < 0.001), maximum basal tumor diameter at initial examination (P = 0.015), maximum apical tumor height (P < 0.001), parallel with cross-linking MCP (P < 0.001), arcs with branching MCP (P = 0.006), loops (P < 0.001), and networks (P < 0.001). Of these, the angiographic documentation of any of the complex MCPs (parallel with cross-linking, arcs with branching, loops, networks, or a combination thereof) showed the strongest association with the time to tumor growth in a Cox proportional hazard model.

CONCLUSIONS

The characteristics of our patient cohort are comparable by clinical and echographic parameters with cohorts for predicting tumor growth, described previously in the literature. In addition, we detected a novel clinical predictor of tumor growth: the confocal ICG angiographic detection of complex MCPs.

An orthotopic model for human uveal melanoma in SCID mice

The microcirculation of primary uveal melanomas, their precursors, and their metastases is distinctive. Medium-sized and even large primary uveal melanomas typically lack significant zones of necrosis, suggesting that either these tumors are relatively well perfused or they are capable of growth in a severely blood-deprived microenvironment. In addition to normal choroidal vessels that are incorporated into nevi and most primary uveal melanomas, aggressive primary and metastatic uveal melanomas tend to contain patterns of extracellular matrix that surround spheroidal or cylindrical packets of tumor cells. Some components of this branching, looping, and interconnected system of matrix may be perfused. It is now known that the generation of this patterning is a characteristic of genetically dysregulated melanoma cells (nonaggressive tumor cells do not form these patterns and melanomas lacking branching, looping, or interconnected matrix patterns tend to follow a relatively indolent course). We developed an orthotopic model of an aggressive human uveal melanoma by injecting suspensions of the primary human choroidal melanoma cell line (OCM1) into the subretinal space of one eye of 20 SCID mice. All mice were examined daily for tumor growth and tumors developed in every eye within 3 weeks of injection. The tumors were characterized by extraocular extension and the development of looping matrix patterns characteristic of those seen in aggressive human uveal melanoma. As in human uveal melanomas, these patterns were perfused by blood in areas. The orthotopic injection of human uveal melanoma cells into the SCID mouse eye generates a model reproducing the matrix-associated microcirculatory patterns of aggressive primary human uveal melanomas. This model can be used to explore the molecular pathogenesis and modulation of this novel circulation in vivo, to facilitate our understanding of the blood flow to these tumors providing insight into perfusion and drug delivery, to enable testing of pharmacologic modulation of pattern formation and intratumoral blood flow, and to refine noninvasive methods such as confocal scanning laser ophthalmoscopy to detect the presence of these patterns by which ophthalmologists might assess the biological behavior of tumors as noninvasive substitute for biopsy.

Control of melanoma morphogenesis, endothelial survival, and perfusion by extracellular matrix

The morphogenetic properties of endothelial cells and melanoma cells were tested under varying matrix quantities and distributions and under constant and saturating levels of growth factors. Aggressive melanoma cells self-assembled into cords vasculogenically only when seeded on thin matrices: nonaggressive melanoma cells did not mimic endothelial cell behavior under any matrix thickness. When buried in matrix, however, aggressive melanoma cells generated looping patterns that contained tumor cells and matrix. These patterns were different topologically and compositionally from cord-like structures or blood vessels but were nevertheless capable of conducting dye by microinjection or passive diffusion. When seeded on three-dimensional cultures of nonaggressive nonpattern-forming melanoma cells, prelabeled endothelial cells attached to, penetrated through, and survived for 2 weeks but failed to form vasculogenic cords. In cocultures containing aggressive melanoma cells, endothelial cells survived briefly but formed short cords only in contact with looping patterns formed by the aggressive tumor cells. Time-lapse recording showed that endothelial cells were lysed upon direct contact with aggressive melanoma cells. Looping patterns identified in human tissue samples were composed ultrastructurally of electron-dense material on either side of a layer of tumor cells; scattered red blood cells were seen in this central cellular layer. By immunohistochemistry, patterns labeled with laminin and fibrinogen colocalized to these looping laminin-positive patterns, suggesting the presence of plasma within these patterns from contiguous leaky tumor vessels. These observations are consistent with the perfusion of these patterns in vitro and with repeated demonstrations of the colocalization of intravenous tracers to looping laminin patterns in animal xenograft models by independent groups. Thus, the distribution and localized quantity of extracellular matrix in aggressive melanomas contributes to the regulation of tumor cell morphogenesis, modulates interactions between tumor cells and endothelial cells, and may contribute to an extravascular matrix-directed circulation.

Imaging the microcirculation of untreated and treated human choroidal melanomas

INTRODUCTION

Histologically demonstrable microcirculation patterns (microcirculation pattern) of human choroidal melanomas have prognostic significance for the patient. We report on our experience in imaging these microcirculation pattern in vivo using simultaneous confocal Fluorescein (FA)- and Indocyaninegreen (ICG) angiography before and after brachytherapy.

PATIENTS AND METHODS

The simultaneously procured confocal FA- and ICG angiograms of 50 patients with untreated choroidal melanomas were studied for the visibility of microcirculation pattern. Patients were also followed with simultaneous FA/ICG after brachytherapy.

RESULTS

Confocal FA disclosed signs of tumor vascularization in 12 (24%) of the 50 examined patients but microcirculation pattern only in 3 patients (6%). In contrast, simultaneously obtained confocal ICG disclosed microcirculation pattern in 47 patients (94%). In 10 (77%) of the 13 patients the tumor microcirculation changed considerably after brachytherapy: Distortion, thickening, thinning, as well as complete obliteration of vessels could be observed.

CONCLUSION

Histologically demonstrated microcirculation pattern can be imaged in vivo. This offers the possibility to assess the likely biologic behavior of the individual tumor without the need for obtaining a cytologic or histologic specimen via enucleation or fine-needle biopsy. Confocal ICG angiogiography images microcirculation pattern better than FA which can be explained by the different absorption-, fluorescence- and exudation-characteristics ICG. Follow-up with confocal ICG of choroidal melanomas after brachytherapy shows different features and allows for visualization of the microcirculation reaction to the treatment which might be a useful tool for studying the effects of future anti-angiogenesis based tumor therapies.

Uveal melanomas express vascular endothelial growth factor and basic fibroblast growth factor and support endothelial cell growth

BACKGROUND

Tumour microvascularity is a significant determinant of prognosis for a large number of different tumours, including uveal melanoma. The development of blood vessels within these and other tumours is partly controlled by soluble pro-angiogenic cytokines, of which basic fibroblast growth factor (bFGF) and vascular endothelial growth factor-A (VEGF) are the best described.

METHODS

Because VEGF has been inconsistently found within uveal melanomas and bFGF is described as an autocrine growth factor in cutaneous melanoma, the authors looked at the expression of these cytokines in uveal melanomas using immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). The cross talk between uveal melanoma cells and endothelial cells was then assessed in an in vitro co-culture model.

RESULTS

While most tumour cells expressed bFGF at the protein level by immunohistochemistry (89%), relatively few (22%) expressed VEGF, and this was of limited extent. All 20 tumours tested by RT-PCR contained mRNA for both bFGF and VEGF. Co-culture experiments using an ATP based bioassay showed that uveal melanomas could support the growth of a rat brain endothelial cell line (GPNT) and human umbilical vein endothelial cells (HUVEC), and that this could be modulated by cytokines and anti-cytokine antibodies.

CONCLUSION

These results suggest that angiogenesis within uveal melanoma may be the result of a complex interplay between endothelial and tumour cells, and that bFGF and VEGF could play a part.

Color Doppler imaging of untreated and irradiated choroidal melanomas

PURPOSE

We examined untreated and irradiated choroidal melanomas with color Doppler imaging (CDI), a noninvasive method providing quantitative measures of blood flow, to determine if the tumor vessel damage associated with irradiation can be detected using this technology.

METHODS

CDI was performed on 122 untreated and 76 previously irradiated tumors using a Q2000 color Doppler ultrasound unit. Spectral analysis was performed on all detectable vascular regions within the tumor to obtain estimates of the peak systolic and end diastolic flow velocities and resistive index ((syst-diast)/syst).

RESULTS

Vessels were detected in 93% of the untreated tumors and in 63% of the treated tumors (p<0.001, X2), and the median number of vascular regions found was higher among untreated tumors (3 vs 1, p=0.001, Wilcoxon Rank Sum). The effect of treatment status on the detection of tumor vessels was significant (p=0.039), controlling for age, sex, largest tumor pretreatment diameter, and tumor height at CDI in a logistic regression model. Mean resistive index was lower in the untreated tumors (0.53 vs 0.58, p=0.0050), controlling for tumor height and other covariates in an analysis of variance.

CONCLUSIONS

On examination with CDI, irradiated tumors had fewer detectable vascular regions and greater resistance to flow than untreated tumors, a pattern consistent with known radiation effects.

Mapping the Location of Prognostically Significant Microcirculatory Patterns in Ciliary Body and Choroidal Melanomas

The microcirculation of choroidal and ciliary body melanomas is remodeled into architecturally distinctive patterns. The presence of two histologic microvascular patterns, networks and parallel vessels with cross-linking, is strongly associated with metastasis. This study was designed to test the hypothesis that networks and parallel vessels with cross-linking patterns are not distributed evenly throughout the tumor. From a set of 234 eyes removed for ciliary body or choroidal melanoma, 152 tumors contained at least one focus of either vascular networks or parallel vessels with cross-linking. Histological cross-sections were digitized and foci of tumor containing these patterns were pseudocolorized so that their location within the periphery or central tumor zone could be mapped. Ciliary body and choroidal melanomas vary widely in size and shape and it is not appropriate to describe the periphery of a tumor as a fixed value because in a small tumor, the periphery thus defined would occupy a larger percent area than in a larger tumor. In this study, the peripheral and central zones of each tumor were described by a function that was constant from tumor to tumor, allowing the width of the peripheral and central zones to vary proportionally with tumor size. Observed counts of vascular patterns per zone were compared statistically with expected counts based upon the percent area occupied by the peripheral and central zones. Discrete foci of networks and parallel with cross-linking vessels are over-represented in the tumor periphery (p < 0.0001).

Expression of VLA-2, VLA-3, and alpha(v) integrin receptors in uveal melanoma: association with microvascular architecture of the tumour and prognostic value

BACKGROUND

The interaction of the integrin receptors with their ligands (collagen, laminin, fibronectin, and others) has a crucial role during the reorganisation of the extracellular matrix and the metastatic process. The presence of particular vascular patterns in uveal melanoma is associated with the development of metastases. There is some evidence that interactions between the tumour cells and the extracellular matrix are responsible for the shape of these patterns.

METHODS

The expression of VLA-2, VLA-3, and alpha(v) integrin receptors was examined by immunohistochemistry on paraffin embedded tumour specimens from 92 uveal melanomas (iris melanomas excluded). Possible correlations between these results and the tumour vascular patterns, the histological features of the tumours as well as the clinical outcome of the patients, were investigated.

RESULTS

The expression of VLA-2 in tumours was associated with the presence of vascular networks (p = 0.05). Tumours with less than 25% VLA-3 positive cells infiltrated the sclera more frequently than those with more than 25% VLA-3 cell positivity (p = 0.05). Tumours expressing less than 50% alpha(v) positive cells were associated with the mixed or epithelioid cell type (p = 0.05) and, with less statistical precision, with the presence of extraocular growth (p = 0.07). The univariate logistic regression analysis showed that the risk of developing metastases within the first 5 years after diagnosis did not depend on the expression of the integrin receptors investigated.

CONCLUSION

The potential biological importance of the associations between integrin expression and the histopathological features of the tumours found in the present study remains to be elucidated in future experiments. The immunohistochemical detection of VLA-2, VLA-3, and alpha(v) integrins had no prognostic value in our preliminary report.

Vasculogenic mimicry and tumor angiogenesis

Tumors require a blood supply for growth and hematogenous dissemination. Much attention has been focused on the role of angiogenesis-the recruitment of new vessels into a tumor from pre-existing vessels. However, angiogenesis may not be the only mechanism by which tumors acquire a microcirculation. Highly aggressive and metastatic melanoma cells are capable of forming highly patterned vascular channels in vitro that are composed of a basement membrane that stains positive with the periodic acid-Schiff (PAS) reagent in the absence of endothelial cells and fibroblasts. These channels formed in vitro are identical morphologically to PAS-positive channels in histological preparations from highly aggressive primary uveal melanomas, in the vertical growth phase of cutaneous melanomas, and in metastatic uveal and cutaneous melanoma. The generation of microvascular channels by genetically deregulated, aggressive tumor cells was termed "vasculogenic mimicry" to emphasize their de novo generation without participation by endothelial cells and independent of angiogenesis. Techniques designed to identify the tumor microcirculation by the staining of endothelial cells may not be applicable to tumors that express vasculogenic mimicry. Although it is not known if therapeutic strategies targeting endothelial cells will be effective in tumors whose blood supply is formed by tumor cells in the absence of angiogenesis, the biomechanical and molecular events that regulate vasculogenic mimicry provide opportunities for the development of novel forms of tumor-targeted treatments. The unique patterning characteristic of vasculogenic mimicry provides an opportunity to design noninvasive imaging techniques to detect highly aggressive neoplasms and their metastases.

Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry

Tissue sections from aggressive human intraocular (uveal) and metastatic cutaneous melanomas generally lack evidence of significant necrosis and contain patterned networks of interconnected loops of extracellular matrix. The matrix that forms these loops or networks may be solid or hollow. Red blood cells have been detected within the hollow channel components of this patterned matrix histologically, and these vascular channel networks have been detected in human tumors angiographically. Endothelial cells were not identified within these matrix-embedded channels by light microscopy, by transmission electron microscopy, or by using an immunohistochemical panel of endothelial cell markers (Factor VIII-related antigen, Ulex, CD31, CD34, and KDR[Flk-1]). Highly invasive primary and metastatic human melanoma cells formed patterned solid and hollow matrix channels (seen in tissue sections of aggressive primary and metastatic human melanomas) in three-dimensional cultures containing Matrigel or dilute Type I collagen, without endothelial cells or fibroblasts. These tumor cell-generated patterned channels conducted dye, highlighting looping patterns visualized angiographically in human tumors. Neither normal melanocytes nor poorly invasive melanoma cells generated these patterned channels in vitro under identical culture conditions, even after the addition of conditioned medium from metastatic pattern-forming melanoma cells, soluble growth factors, or regimes of hypoxia. Highly invasive and metastatic human melanoma cells, but not poorly invasive melanoma cells, contracted and remodeled floating hydrated gels, providing a biomechanical explanation for the generation of microvessels in vitro. cDNA microarray analysis of highly invasive versus poorly invasive melanoma tumor cells confirmed a genetic reversion to a pluripotent embryonic-like genotype in the highly aggressive melanoma cells. These observations strongly suggest that aggressive melanoma cells may generate vascular channels that facilitate tumor perfusion independent of tumor angiogenesis.

Evaluation of the human choroidal melanoma rabbit model for studying microcirculation patterns with confocal ICG and histology

The aim of this study was to develop consistently focal elevated choroidal masses of human choroidal melanoma in immunosuppressed rabbits and to correlate the visualization of prognostically significant microcirculation patterns from confocal indocyanine green angiography with histologic microcirculation patterns. A human choroidal melanoma cell line (OCM1) was implanted in the choroid of 40 rabbit eyes using three different techniques: transscleral choroidal injection of a cell suspension, injection of a cell suspension in a surgically induced cyclodialysis cleft, and implantation of solid tumor fragments in a surgically induced cyclodialysis cleft. The rabbits were immunosuppressed with daily injections of Cyclosporin A to prevent host versus graft reaction. The eyes were studied weekly with indirect ophthalmoscopy and fundus photography to monitor tumor growth and indocyanine green angiography using a confocal scanning laser ophthalmoscope to identify microcirculation patterns in vivo and correlate these findings with the histologic demonstration of tumor microcirculation patterns. A tumor mass was identified by indirect ophthalmoscopy in 16 of the 40 implanted rabbit eyes (40%). Each of these tumors was confirmed histologically to represent a focal elevated choroidal mass. All 16 elevated choroidal masses grow in eyes in which solid tumor fragments were implanted. In total, a melanoma was identified histologically in 28 of the implanted 40 eyes (70%). In addition to the 16 eyes where the melanoma appeared as a focal elevated choroidal mass, 4 eyes contained a focal elevated mass in the sclera and 8 eyes contained a flat choroidal tumor. Histologically, microcirculation patterns were identified only in the 16 eyes with focal elevated choroidal masses. Confocal indocyanine green angiography imaged microcirculation patterns in 13 of these 16 eyes (81%). The surgical implantation of small solid fragments of human choroidal melanoma in immunosuppressed rabbit eyes provides the best method to consistently obtain focal elevated choroidal masses. These focal elevated choroidal masses resemble booth the localization and the growth pattern of choroidal melanomas in humans. In addition, they also contain microcirculation patterns similar to those seen in humans that are detectable with confocal indocyanine green angiography. The use of indocyanine green angiography with this animal model may be especially useful in designing and evaluating anti-microcirculation treatments directed at uveal melanoma.