The preneoplastic state in mouse mammary tumorigenesis.

It is widely accepted that neoplasms in epithelial organs arise via multiple intermediate stages (1—3). This concept has been extensively developed over the past 30 years and is based upon both clinical and experimental observations in practically all major epithelial organs. The intermediate stages have been labeled with various terms, although the terms preneoplastic or premalignant have been used most frequently. It is the aim of this commentary to discuss the preneoplastic state in the mouse mammary gland. It is hoped that the review will invite discussion and comment, stimulate new ideas and experimental approaches, and attract new participants into this research area. The time is appropriate for such a review in light of the new methodologies which have been developed in the area of mammary gland research over the past 10 years and the opportunity to apply newer molecular biology approaches to examine basic questions in mammary carcinogenesis.