Microcomputed tomography (micro‐CT) analysis showed extensive osteosarcoma with sclerosis and cortical destruction in the femurs of 7‐month‐old Ctsk‐Cre;Trp53f/f/Rb1f/f mice compared to that in the Ctsk‐Cre control mice (Figure 1C). Here, CTSK is linked to osteosarcoma.