MORPHOGENESIS OF ESOPHAGEAL-CARCINOMA INDUCED BY N-METHYL-N'-NITRO-N-NITROSOGUANIDINE IN THE HOUSE MUSK SHREW, SUNCUS-MURINUS (INSECTIVORA)

The histological changes occurring in the esophageal mucosa of shrews (Suncus murinus) after N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) tre atment were investigated sequentially. Six-week-old female shrews were given a 50 mu g/ml MNNG solution as drinking water for 30 weeks, and 5 selected at random were killed at 10 and 20 weeks of age, and therea fter at 5-week intervals until 45 weeks of age. Controls were killed a t 45 weeks of age, The MNNG-induced esophageal lesion in shrews began from basal cell hyperplasia at 20 weeks of age, followed by dysplasia occurring at 25 weeks of age, then progressed toward intraepithelial c arcinoma to invasive squamous cell carcinoma at 35 weeks of age. Appar ent sequential dysplasia carcinoma transition was seen. Papillomas wer e seen from 25 weeks of age but there was no evidence of papilloma-car cinoma sequence. Five MNNG-untreated shrews killed at the end of the e xperiment were free of esophageal tumors.