Figure 4

Establishment of fibrosarcoma by exposure of animals to benzo (a) pyrene. Administration of benzo (a) pyrene (250 µg/animal, subcutaneously) into the flanks of the animals resulted in successful tumor induction in at least 90 % of the animals and no tumor development in 10 % of the animals. The tumor-bearing animals were killed by cervical dislocation and fixed in 10 % formaldehyde solution. Subsequently tissues were excised and sections were prepared after standard HE staining of 12-mm-thin sections. (A) Photomicrograph from tumor showing zone of necrosis, increased vascularization and hemorrhage. Large numbers of hyperchromatic mesenchymal cells with features of fibrosarcoma are present. Some hyperchromatic cells are arranged in glandular form. (B) Photomicrograph from tumor showing soft tissue sarcoma with large pleomorphic, hyperchromatic spindle-shaped cells with anisonucleosis and irregularly dispersed chromatin. Some inflammatory cells can also be seen.