Reexamination of histological findings of ileal sarcomas induced in rats given diet containing bracken fern.

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.