Aggressive papillomas and soft tissue sarcomas inAID-Cre-YFP Kras^G12D Arf^−/− mice.

A) Gross appearance of progressive tumors affecting an AID-Cre-YFP Kras^G12D Arf ^−/− mouse at 13 weeks of age. Tumors progressed rapidly from smaller papillomas on the ventral neck. B) Control AID-Cre-YFP Arf ^−/− control mouse at 13 weeks appears normal. Hematoxalin & eosin stains of C) spleen section from AID-Cre-YFP Kras^G12D Arf ^−/− shows disruption of splenic architecture by inflammatory cells; D) spleen section from AID-Cre-YFP Arf ^−/− control appears normal; and E) section of subcutaneous sarcoma from AID-Cre-YFP Kras^G12D Arf ^−/− at 13 weeks shows spindle shaped cells consistent with soft tissue sarcoma. Original magnification, x10 (spleen); x40 (sarcoma). Scale bar: 200 um (spleen); 50 um (sarcoma). Tumor development was uniform in AID-Cre-YFP Kras^G12D Arf ^−/− mice and did not require any tumor-promoting treatment. Representative images are shown.