Figure 1. Core biopsy of a pulmonary pleural-based lesion revealed benign tissue consistent with lymphangioma. The CD31 antibody immunohistochemical stains (A, magnification x200, and B, x400) reveal the specificity for platelet endothelial cell adhesion molecule, confirming the endothelial nature of this lesion. The elastin stain (C, x200) highlights elastin protein in the walls of the vessels, suggesting the presence of a vascular structure with elastic tissue. The standard hematoxylin and eosin stain (D) is shown at x100.