The FEM generated from MRI data represents the breast in the prone position because it assumes the configuration of the patient during MRI acquisition. Yet, during the surgery simulation work-flow, some stages require the model to represent the patient in different positions. As consequence, two explicit pose transformations occur (Figure 2D,F), and a third one takes place during the wound healing step (Figure 2G). In detail, MRI data is acquired with the patient lying in prone position (Figure 3A), but the upright position (Figure 3G) is the most suitable pose to evaluate the natural shape of breast and, consequently, its deformations. Thus, wound healing results are outputted in the upright position (Figure 3F). On the other hand, BCS is performed with the patient lying in supine position (Figure 3D), implying that any surgical planning activity, such as the definition of tumor characteristics and the volume to excise, should be done in this position. The multiscale model used for surgery simulation can estimate pose transformations by computing the unloaded state (a gravity free reference state) and re-applying gravity stress in the desired direction. As result, the FEM, constructed in prone position, is converted to an unloaded state (Figure 3C), from which both supine (Figure 3D) and pre-surgery upright position (Figure 3G) can be estimated. The tumor is defined in supine position (Figure 3D) and the FEM is again converted from supine to the unloaded state (Figure 3E), where the wound healing simulation is carried out. The simulation result (post-surgery data) is returned in upright position (Figure 3F). With this pose transformation pipeline, both pre- and post-surgery data are represented in the upright position, and can be directly compared for predicting shape deformations caused by BCS.