RAC1 and skin neoplasm: More recently, an in vivo study also revealed that epidermis-specific activation of Rac1 in a transgenic mouse model of differentiated sebaceous adenomas, while not affecting tumor initiation, was associated with the formation of less differentiated tumors that resemble malignant sebaceous tumors, thereby implicating Rac1 in the malignant progression of sebaceous skin tumors.67