Fig. 1

(1) Representative images of histological parameters evaluated in this study. a Schematic figure of papillary fusion. b Delicate papillae with no fusion. c Papillary fusion (the arrow marks an imaginary fusion line). d Confluent fusion of papillae. e Presence of umbrella cells (arrowhead). f Absence of umbrella cells. g Schematic figure for the estimation of cell density based on the distance between cells. h Cell density score 1. i Cell density score 2. j Cell density score 3. k Discohesiveness (l). Nuclear pleomorphism category 4 based on a difference between the smallest and the biggest nucleus of the tumor cells of about 20-fold. m Multinucleated giant cells. n Mild nuclear hyperchromasia. o Moderate nuclear hyperchromasia. p Severe nuclear hyperchromasia. q Polarity loss score 2