Thioacetamide-induced cataract with invasive proliferation of the lens epithelium in rainbow trout.

Cataracts developed in 90% of rainbow trout maintained on a thioacetamide diet for prolonged periods of time. The most striking feature in the histology of these lenses was a massive proliferation of the lens epithelium and its transforma tion to a pleomorphic cell mass which sometimes replaced a great portion of the anterior lens cortex. The profuse invasion of the epithelial cells, their disorganization, and the presence of forms similar to Darier cells and epithelial pearls suggest a tumorous growth pattern. The relation of the epithelial proliferation to fiber damage is not clear nor is the role of the carcinogenic properties of thio acetamide in the development of the lens pathology.