Confocal microscope analysis and tridimensional reconstruction of papillary thyroid carcinoma nuclei

Nuclei of papillary thyroid carcinoma (PTC) are characterised by diagnostic morphological features, which include optically clear nuclei, irregular nuclear profile, pseudoinclusions and grooves. In the present study, such nuclear features were analysed by means of confocal microscopy using anti-lamin B antibodies to outline the nuclear membrane. Parallel sections of the nucleus, produced by confocal microscope analysis, showed that the nuclear shape is markedly irregular with profound invaginations, clefts and tunnel-like structures, which correspond to the "grooves" and "holes" detectable using light microscopy, respectively. A tridimensional (3-D) model of the nuclei, obtained by a computer-based reconstruction of confocal microscope images, showed, in the vast majority of PTC cells, nuclei with crateriform areas, clefts and even tunnel-like structures "piercing" the whole nuclear thickness. By rotating these models in space, it became evident that the holes and grooves seen in light microscopy correspond to invaginations and tunnels, depending on the viewpoint. In conclusion, this is the first application of confocal microscopy and tridimensional reconstruction to the study of nuclear morphology of PTC and of tumours in general. The light microscopic appearance of PTC nuclei, so familiar to pathologists, is, therefore, due to profound remodelling of the nuclear shape with invaginations and tunnels, which appear as either grooves or holes, according to the viewpoint.