Figure 3.

Relationship between malignancy and the degree of placentation in mammals.

Mammalian placentas can be classified on the degree of invasiveness. Here we plotted the relationship between malignancy and placenta invasiveness. Degree of placentation was grouped from left to right, with marsupials on the far left representing rudimentary yolk-sac placentas, then Eutherian placenta classifications: epitheliochorial (least invasive), endotheliochorial (intermediate invasive) and hemochorial (most invasive). We found no association between degree of placentation and malignancy or neoplasia (also see Supplementary Fig. S5).