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 .