Abstract
The ileal sarcomas induced in rats given diet containing bracken fern were examined microscopically and electron microscopically. These ileal sarcomas, which were induced at high incidence (80%-44%), have previously been identified as spindle cell fibrosarcomas. However, studies showed that they should be diagnosed as malignant fibrous histiocytomas (MFH) being classified into the following four histological types; fibrous, pleomorphic, giant cell and myxoid type. No types of sarcomas other than MFH were found in the ileum.