3. Pathobiologic Events Associated with
Ductal Carcinoma in Situ.
The molecular, cellular, and pathological processes
that occur in the transformation from healthy
tissue to preinvasive lesions, such as ductal
carcinoma in situ, to breast cancer are shown.
The majority of the changes that give rise to
cancer, including the accumulation of genetic
changes, oncogene expression, and the loss of
normal cell-cycle regulation, appear to have occurred
by the time ductal carcinoma in situ is present.
Most of the clinical features of a subsequent
invasive breast cancer are already determined
at this stage, although additional events, including
tissue invasion and changes in the surrounding
stroma, characterize the invasive tumor .