A single solid with one material is an over simplification of the anatomy of a breast.
Each breast has 15 to 20 sections, called lobes arranged like the petals of a daisy.
Each lobe has many smaller structures called lobules.
The lobes and lobules are linked by thin tubes called ducts that lead to the nipple.
Fat fills the spaces between lobules and ducts and skin covers the internal structure.
If you had a detailed model of the anatomy with appropriate material properties for each type of tissue, then you might see a more realistic response to gravity.
Where did you obtain the initial shape of the breast, which represents the shape without gravity? Any 3D scan on earth would be in the presence of gravity. Ansys can do inverse solving which takes a deformed shape as input along with the load (gravity) and computes the shape with no load. That is the shape you want to start with.