Figure 42.

Labeling of mitotic cells by Ki-67 immunostaining in the pharyngeal tonsil (inset: high-power view). A high-molecular-weight polymer reagent in the EnVision system provokes a false-negative result for Ki-67 nuclear labeling of proliferative cells. Only mitotic cells are labeled. It seems that the huge molecules of the secondary reagent cannot reach the non-mitotic proliferative cells but do reach the mitotic cells lacking the nuclear membrane.