Fig. 1

Histological examination of biopsy specimens from lung tumours. a Photomicrograph of haematoxylin and eosin-stained tumour section showing small cells with scant cytoplasm and granular nuclear chromatin (objective lens magnification, ×40). b Photomicrograph of tumour section immunostained for Ki-67 using the MIB-1 antibody clone, showing positive (green dots) or negative (red dots) cells based on pixel colour intensity. Some cells weakly stained brown were automatically assessed as not positive by the cell counting software