“…However, many previous studies specify a classical one-phase Stefan condition [23] at the free boundary, where the rate of expansion of the free boundary is assumed proportional to the spatial gradient of the density without strong biological justification, or the evolution of the tissue length is specified according to experimental observations [24, 25, 26, 27, 28, 29]. Here, the evolution of the tissue boundary arises naturally from the cell-scale processes of cell proliferation, mechanical cellular relaxation [30, 31, 32], and cell detachment.…”