Comparing vasculogenic mimicry with endothelial cell-lined vessels: techniques for 3D reconstruction and quantitative...

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.