Interstitial cell carcinomas of the testis in Balb/C male mice ingesting methoxychlor.

Balb/c and C3H strains male and female mice ingested 750 ppm methoxychlor or 100 ppm DDT in the diet for 2 years. Balb/c strain male mice ingesting methoxychlor developed a highly significant incidence of interstitial cell carcinomas of the testis. Balb/c strain male mice ingesting DDT and C3H strain male mice receiving methoxychlor or DDT did not have testicular tumors. The carcinomas of the testis varied from well-differentiated to poorly differentiated and undifferentiated and were capable of metastasis. Carcinomas of the testis have been described in Balb/c strain male mice, but not C3H, given estrogens. The carcinogenicity for testis of Balb/c strain male mice is most likely related to the estrogenic activity of methoxychlor.