As shown in the research, SMAD4 is a well-characterized tumor suppressor that participates in carcinogenesis through numerous mechanisms, such as the induction of cell cycle arrest, apoptosis, angiogenesis, and the EMT [89,90]; however, very few studies have looked into the role and mechanism of action of SMAD4 in endometriosis. The gene discussed is SMAD4; the disease is neoplasm.