Abstract
Cancer progression and dissemination are the outcome of a complex interplay between cancer cells and the surrounding microenvironment. Therefore, the three-dimensional features of tumor parenchyma-stroma architecture should be integrated in the histopathological diagnosis of solid tumor malignancy. In order to elucidate the diversity of tumor invasion patterns in the 3D microenvironment of tongue squamous cell carcinoma (SCC), we routinely conducted histology-based 3D reconstruction using 100-250 serial histological sections (4-μm thick). The basic procedure for 3D reconstruction is the preparation of serial sections using a paraffin tissue microarray in combination with immuno-staining of tissues, computer-assisted color segmentation of tumor parenchyma and stroma, and alignment and superposition of digitized images. The resulting 3D constructs provided sufficient spatial resolution to segregate individual cells and to validate the continuity or separation of carcinoma cells at the deepest invasion front. Observations in the 3D space revealed discrete SCC architectures that were classified into several categories from bulky masses with pushing border to infiltrating islands or clusters. Of particular importance in the malignancy grading assessment based on the histopathological characteristics of the deep invasive front of SCC, an anastomosing network of tumor strands in tissue volume may appear in 2D histological sections as discontinuous segments of small foci. Indeed, our experience proved that 3D reconstruction is an essential tool to validate the nature of continuity or sequestration of carcinoma cells and to collect quantitative information as to the number and size distribution of invading carcinoma foci into the surrounding microenvironment.
