Carcinogenesis would appear distinct from a conceptual framework implicating progression from a series of truly hyperplastic ductal lesions of the breast. An a priori concept of established predetermined evolution of the single large duct papilloma as a benign lesion would contrast with a concept of possible malignant transformation of atypical hyperplasia of breast ducts. Characteristics of a process of transformation in the added given context of attributes of a specific cell type of origin would further define systems of change in terms of stem cells that are biologically distinct from cell of origin of specific organs or tissues. It is only in terms of such stem-like cells that one would better explain proliferative and metastatic potential for various malignant lesions. These may either arise denovo or else evolve in a context of previous insitu proliferation of cells that become progressively more atypical morphologically and more biologically active with increase of the lesion. Transitory and straddling cell forms would alternatively adopt attributes of a stem-like type in the origin and subsequent course of development of desuppressed progression of a malignant neoplasm.