TGFB1 and squamous cell carcinoma: Here, we have taken advantage of a mouse model that develops spontaneous tumors at their anorectal transition zone upon loss of TGFβ signaling, which recapitulates invasive human anogenital squamous cell carcinoma, to define the cells and mechanisms by which these tumors grow and to identify the signaling pathways upon which they rely when undergoing metastasis.