Tumor cell mitotic index is diminished in footpad tumors derived from plasminogen-deficient mice relative to control animals. Mitotic figures (arrowheads) were easily discernible in hematoxylin-eosin–stained sections of footpad tumors from control (A) and plasminogen-deficient (B) mice. (C) Quantitative analysis of mitotic indices within footpad tumors of mice with single and combined deficits in plasminogen and fibrinogen. The mitotic index observed in plasminogen-deficient (*) mice was significantly less than that observed in control animals (P < .02). In contrast, no significant difference in mitotic index was observed in comparative analyses of control animals and plasminogen-deficient mice that also lacked fibrinogen (P > .8). Mitotic indices were also similar in control and fibrinogen-deficient mice (P > .9). All P values were established using the Mann-Whitney U test. Error bars indicate standard deviation from the mean value for 6 mice.