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

The prognostic implication of visual acuity at the time of uveal melanoma diagnosis

BACKGROUND

Visual outcomes after primary tumour treatment of uveal melanoma (UM) have been investigated repeatedly. This study evaluates the correlation between best-corrected visual acuity (BCVA) before treatment with clinicopathological factors and patient survival.

SUBJECTS/METHODS

Pre-treatment BCVA was examined in relation to tumour dimensions and location, and survival in a retrospective cohort of 1809 patients who underwent plaque brachytherapy. BCVA was also correlated to tumour histological factors in a second cohort of 137 enucleated eyes.

RESULTS

The mean BCVA of the tumour eye prior to plaque brachytherapy was LogMAR 0.42 (SD 0.46). Patients with low BCVA (LogMAR ≥ 1.00) did not differ in age (p = 0.19) and had similar frequency of ciliary body involvement (p = 0.99) but had tumours with greater apical thickness (p < 0.0001), greater diameter (p < 0.0001) and shorter distance to the optic disc and fovea (p < 0.0001). There were no significant relations between low BCVA and any of 13 examined tumour histological factors at a Bonferroni-corrected significance level (p > 0.004). Patients with low BCVA had greater incidence of UM-related mortality in competing risk analysis (p = 0.0019) and shorter overall survival (p < 0.0001). Low BCVA was also associated with increased hazard ratio (HR) for UM-related mortality in univariate analysis (HR 1.5, 95% confidence interval 1.2 to 1.9), but not in multivariate analysis with tumour size and location as covariates.

CONCLUSIONS

UM patients with low BCVA before primary tumour treatment have a worse prognosis, likely related to increased tumour dimensions. Future studies should examine the prognostic significance of BCVA in relation to macula-involving retinal detachment and genetic factors.

Artifacts and main lesions in fetal ocular histology

Histological artifacts in fetal eyes can involve different tissues and can be related to mechanical or autolytic lesions, fixation, the cause of death or the cutting technique. Knowing the causes, effects and appearance of artifacts allow the minimization of the risk of avoidable artifacts and help distinguish them from "true" pathological lesions. We describe these different types of artifacts and specifically analyze their involvement in different tissue structures of the eye. We compare them with primary fetal ocular lesions. Given the wide variety of artifacts, the identification of lesions in fetal eyes must be done with caution, since differentiating true lesions from artifacts requires some experience and relies on both macroscopic examination and microscopic analyses, with ideally comparisons with references' images of normal tissues of the same gestational age.

Vasculogenic mimicry correlates to presenting symptoms and mortality in uveal melanoma

PURPOSE

Fluid-conducting extracellular matrix patterns known as vasculogenic mimicry (VM) have been associated with poor prognosis in uveal melanoma and other cancers. We investigate the correlations between VM, presenting symptoms, mortality, and the area density of periodic acid-Schiff positive histological patterns (PAS density).

METHODS

Sixty-nine patients that underwent enucleation for uveal melanoma between 2000 and 2007 were included. Clinicopathological parameters presenting symptoms and outcomes were collected. Histological tumor sections were evaluated for VM and PAS density was quantified with digital image analysis.

RESULTS

Thirty-four patients (49%) presented with blurred vision. 18 (26%) with a shadow in the visual field, 7 (10%) with photopsia and/or floaters, and 2 (3%) with metamorphopsia. Nine patients (13%) had no symptoms at all. Median follow-up was 16.7 years (SD 2.6). A shadow in the visual field, but no other symptom, was positively correlated with the presence of VM (φ 0.70, p < 0.001) and greater PAS density (p < 0.001). In multivariate regression, retinal detachment (RD), presence of VM, and PAS density ≥ median were independent predictors of a shadow, but not tumor distance to the macula, tumor apical thickness, tumor diameter, or ciliary body engagement. The presence of VM was associated with significantly shorter cumulative disease-specific survival (Wilcoxon p = 0.04), but not PAS density ≥ median, presenting symptoms or RD (p > 0.28).

CONCLUSION

Tumors from uveal melanoma patients that report a visual field shadow are likely to display VM and greater PAS density, likely explaining the previously reported association between this symptom and poor prognosis.

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.

Tumor cell plasticity in uveal melanoma: microenvironment directed dampening of the invasive and metastatic genotype and phenotype accompanies the generation of vasculogenic mimicry patterns

The histological detection of laminin-rich vasculogenic mimicry patterns in human primary uveal melanomas is associated with death from metastases. We therefore hypothesized that highly invasive uveal melanoma cells forming vasculogenic mimicry patterns after exposure to a laminin-rich three-dimensional microenvironment would differentially express genes associated with invasive and metastatic behavior. However, we discovered that genes associated with differentiation (GDF15 and ATF3) and suppression of proliferation (CDKNa1/p21) were up-regulated in highly invasive uveal melanoma cells forming vasculogenic mimicry patterns, and genes associated with promotion of invasive and metastatic behavior such as CD44, CCNE2 (cyclin E2), THBS1 (thrombospondin 1), and CSPG2 (chondroitin sulfate proteoglycan; versican) were down-regulated. After forming vasculogenic mimicry patterns, uveal melanoma cells invaded only short distances, failed to replicate, and changed morphologically from the invasive epithelioid to the indolent spindle A phenotype. In human tissue samples, uveal melanoma cells within vasculogenic mimicry patterns assumed the spindle A morphology, and the expression of Ki67 was significantly reduced in adjacent melanoma cells. Thus, the generation of vasculogenic mimicry patterns is accompanied by dampening of the invasive and metastatic uveal melanoma genotype and phenotype and underscores the plasticity of these cells in response to cues from the microenvironment.

Osteopontin expression and serum levels in metastatic uveal melanoma: a pilot study

PURPOSE

This was a pilot study conducted to examine the expression of osteopontin in uveal melanoma and to determine whether serum osteopontin can be used in detecting metastatic uveal melanoma.

METHODS

Osteopontin mRNA was measured in three uveal melanoma cell lines of various invasive potential by real-time PCR. Tissue sections of primary and metastatic uveal melanomas were stained for osteopontin. Serum osteopontin levels were measured by ELISA assays in 15 patients with metastatic uveal melanoma and in 37 patients who were disease-free for at least 10 years after treatment of the primary tumor. Paired serum samples drawn from eight patients before and after development of metastasis were analyzed.

RESULTS

By real-time PCR, highly invasive primary and metastatic uveal melanoma cells expressed 6- and 250-fold excess osteopontin mRNA, respectively, compared with poorly invasive primary uveal melanoma cells. Tissue sections of primary uveal melanomas lacking looping vasculogenic mimicry patterns either did not stain for osteopontin or exhibited weak, diffuse staining. In primary melanomas containing looping vasculogenic mimicry patterns, strong osteopontin staining was detected in the tumor periphery where patterns were located. Diffuse strong expression of osteopontin was detected in eight samples of uveal melanomas metastatic to the liver. Serum osteopontin levels were significantly higher in patients with metastatic uveal melanoma than in patients who had been disease free for at least 10 years after treatment (P = 0.0001) or in age-matched control subjects. Serum osteopontin levels were significantly higher (P = 0.008) after metastasis than before the detection of metastasis in eight patients. When a cutoff of 10 ng/mL was used, the sensitivity and specificity of serum osteopontin in detecting metastatic melanoma was 87.5%, and the area under the receiver operator characteristic curve was 96%.

CONCLUSIONS

Osteopontin is expressed diffusely in tissue sections of hepatic metastases from uveal melanoma, and increased serum osteopontin levels correlate with melanoma metastasis to the liver with high specificity and sensitivity.

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.

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.

Spectral parameter imaging for detection of prognostically significant histologic features in uveal melanoma

Specific extracellular matrix patterns in uveal melanoma are associated with metastatic risk. The laminin-rich composition and dimensions (on the order of a wavelength or less) of these structures suggest that acoustic backscatter might be affected by their presence. In this study, 10-MHz radiofrequency (RF) ultrasound (US) data were acquired before surgical removal of 117 eyes with uveal malignant melanoma. Histologic sections were evaluated for the presence of matrix patterns and acoustic backscatter was characterized using calibrated spectrum analysis. Statistical correlations between acoustic and histologic patterns were determined and linear discriminant analysis (LDA) and radial basis networks (RBN) were used to develop classification models for histologically based risk groups. Statistically significant correlations were found between acoustic parameters and the presence of histologic matrix-rich patterns. Retrospective classification accuracies of 74.4% and 78.6% were obtained with LDA and RBN, respectively. Leave-one-out analyses indicated estimated predictive accuracies of 71.8% and 75.0% for LDA and RBN, respectively.

Tumor sinuses- vascular channels

The existence of tumor cell-lined sinuses (vascular channels) in various experimental and human cancer is known for almost a half a century described by a Hungarian pathologist, Béla Kellner. Meanwhile, even the existence as well as the pathomechanism and the possible functional significance of these sinuses are heavily challenged in the recent literature. Ultrastructural studies however provide evidence for the presence of tumor cell-lined sinuses in human melanoma and breast cancer. The generation of such sinuses can be suggested in two ways: by de novoformation, when tumor cells recapitulate an embryonic geno- and phenotype by reexpressing endothelial genes or by a secondary mechanism, where the incorporated microvessels degenerate due to the predominant expression of anti-angiogenic factors. Literature data are available for the potential diagnostic and clinical significance of the tumor sinuses (vascular channels) stimulating further studies on this issue.

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.