Gauging metastatic propensity is crucial as it impacts decision making in oncology (e.g. whether a patient should receive surgery immediately or neoadjuvant chemotherapy). Interstitial fluid pressure (IFP) is known to correlate with microvascular invasion, a proxy for metastatic potential. However, no current imaging biomarkers correlate with this. We present a method to noninvasively calculate a total tumor pressure (which IFP contributes to). The method reconstructs pressure via nonlinear biomechanics and MR Elastography and is validated in simulations and phantoms. Elevated pressure values from a cohort of 16 breast cancer patients correlate with lymphovascular invasion possibly providing a much sought-after biomarker.