Injection site tumours and preceding pathological changes in rats treated subcutaneously with surfactants and carcinogens.

The sequential histological changes and neoplastic response occurring in the subcutaneous tissue of rats after injection of surfactants or carcinogens were compared. Twice weekly subcutaneous injections of the surfactants Blue VRS and Light Green SF elicited a deranged connective tissue repair with continued proliferation of fibroblasts and extensive collagen desposition. In contrast, the carcinogens N-methyl-N-nitrosourea (MNU) and N-nitroquinoline-N-oxide (NQO) appeared to inhibit connective tissue repair and produce morphologically abnormal fibroblasts. The spectrum of neoplastic response was also found to differ. Surfactants gave rise to local sarcomata only after about 47 weeks, whereas carcinogens produced local sarcomata and adenocarcinomata after 20 and 12 weeks respectively.