EARLY DEVELOPMENT OF INJECTION-SITE SARCOMAS IN RATS - A STUDY OF TUMOURS INDUCED BY IRON-DEXTRAN

Early stages in the development of sarcomas have been studied in 60 young Wistar rats, treated with 20 once-weekly intramuscular injections of iron-dextran. Thirty-five control animals received 20 once-weekly intramuscular injections of physiological saline. The rats were killed in pairs, mostly at 4-weekly intervals, between the 4th and 64th weeks after the beginning of the experiment. Twenty-five of the 60 test animals developed local sarcomas-17 rats with macroscopic tumours only, 3 rats with macroscopic and microscopic sarcomas, and 5 rats with microscopic lesions only. The microscopic lesions appeared first as “clear zones” between dense accumulations of siderophages and consisted of atypical spindle cells in a pool of amorphous ground substance. Such foci became progressively cellular and pleomorphic and eventually showed signs of extension into the surrounding tissues. The macroscopic sarcomas produced were similar to the spindle cell and pleomorphic neoplasms frequently reported in the past in rats injected with iron-dextran. Reasons for regarding these foci of atypical spindle cells as early sarcomas are discussed and their close resemblance to lesions produced in the subcutaneous tissues of the rat with a number of other carcinogens is emphasised. © 1969, The British Empire Cancer Campaign for Research. All rights reserved.