Correlation between morphology of colonies formed by human thyroid tumor cells in collagen gel culture and invasive ability.

Two different types of colonies from human thyroid papillary carcinomas were observed in collagen gel culture. One was a branching type, with many three-dimensional outgrowths. The other was a spherical type, with no outgrowths. As viewed by electron microscopy, the tumor cells of spherical-type colonies had more microvilli on their surfaces than did cells in the branching-type colonies. Histochemically, the tumor cells of spherical-type colonies had stronger positive reactions than did tumor cells of branching-type colonies. This suggests that tumor cells of spherical-type colonies have a higher potential for dissemination and invasion than do tumor cells of branching-type colonies. In fact, cases with higher percentages of spherical-type colonies could show extracapsular invasion histopathologically. Our results indicate that collagen gel culture is a useful method for studying the heterogeneity of tumor cells as well as their invasive ability in vitro.