Aggressive fibromatosis, also known as desmoid tumor, is specific and relatively rarely occuring disease. It belongs to heterogenous group of soft tissue tumors. Originally, it arises from fibroblasts with monoclonal proliferation derived from fibro-aponeurotic tissue with typical local invasive spreading without metastatic tendency. Increased amount of knowledge about the role of the APC gene and its protein product in FAP play an important role in revealing the molecular nature of desmoid tumors. In general, we can conclude that the β-catenin dysregulation is the key player of the FAP associated desmoid tumor onset. The Wingless/Wnt cascade plays a crucial role in the pathogenesis of aggressive fibromatosis. However, it has not been definitely proven that the mutations of APC or β-catenin genes are the trigger mechanisms. The research outcome can pave the way for using target biological therapy in routine practice in patients with aggressive fibromatosis in the future.