Interpretation of Rodent Hepatocellular Proliferative Alterations and Hepatocellular Tumors in Chemical Safety Assessment ,

Benign and malignant liver tumors have been frequently observed in National Cancer Institute/National Toxicology Program rodent carcinogenesis bioassays using Fischer 344 rats and B6C3F1 mice. A multilayered pathology review process enhances consistency and accuracy of the histologic diagnoses. All data, including statistically analyzed tumor prevalences, are ultimately reviewed by a multidisciplinary team of scientists for judgment regarding the carcinogenicity of the chemical. Rationale for interpretation of hepatocellular alterations is illustrated with results from the recently completed NCI/NTP bioassays of di(2-ethylhexyl)phthalate, C.I. Disperse Yellow 3, C.I. Solvent Yellow 14, and pentachloroethane.