This raises a fundamental question: What prevents or permits oncogenic cells from expanding at the earliest stages of cancer initiation? We demonstrate that this heterotypic interfacial tension is a key determinant of mutant cluster morphology and dynamics. When interfacial tension between wild-type and mutant populations was positive, mutant clusters shrunk into circular aggregates and stayed constrained. In contrast, a negative interfacial tension resulted in irregular, protrusive clusters that failed to compact and kept growing. Future studies should investigate how targeting specific signaling networks or cytoskeletal components influences interfacial tension and whether modulating these factors could provide therapeutic benefits.