Figure 2

Tissue architecture and distribution of cathepsin B in thyroid carcinoma in situ. Micrographs of haematoxylin and eosin stained tissue of thyroid tissue derived from patients with papillary (A) and follicular (D) thyroid carcinoma (PTC and FTC, respectively) was inspected by brightfield microscopy. PTC tissue displayed areas with intact follicle structures (A) as well as areas with a disorganized tissue structure (A, dashed arrows). In addition, PTC tissue displayed fibrovascular cores (A). FTC tissue also displayed areas with intact follicle structures as well as areas with a disorganized tissue structure (D, dashed arrows). Merged (B, C, E, F), single channel fluorescence and corresponding phase contrast micrographs (left panels) taken with the confocal laser scanning microscope of thyroid tissue from patients with PTC or FTC showing the endogenous distribution of cathepsin B (green, left panels, top). The nuclei were visualized through DRAQ5™ counter-staining (blue, left panels, middle). Note that cathepsin B was localized to vesicles close to the apical plasma membrane (arrows) in non-neoplastic areas of thyroid carcinoma tissue (B and E, respectively). Cathepsin B distribution was different in the disorganized, neoplastic areas of thyroid carcinoma tissue (C and F). The protease was immunolocalized to vesicles scattered in the cell periphery along the basal and lateral plasma membrane domains as well as scattered throughout the cytosol (C and F, arrowheads). Nuclei of cells in neoplastic areas displayed an abnormal morphology (C and F, open arrowheads). Follicle lumina are denoted by asterisks. Scale bars represent 50 µm in A and D, and 20 µm in B, C, E, and F.