We present a numerical scheme used to investigate a mathematical model of tumor growth which incorporates multiple disparate timescales. We simulate the model with different initial data. The initial conditions explored herein correspond to a small remnant of tumor tissue left after surgical resection. Our results indicate that tumor regrowth begins at the pre-surgery tumor-healthy tissue interface and penetrates back into the original tumor area. This growth is rate-limited by the reformation of the tumor vascular network.