Stromal metachromasia: a marker for areas of incipient invasion in ductal carcinoma of the breast?

This morphological study of small ducts with in situ breast carcinoma demonstrates the changes that occur in the adjacent stroma when it stains metachromatically with toluidine blue. They are indistinguishable from those reported in areas with infiltrative tumour growth, and are accompanied by progressive damage to the duct wall. The latter may be destroyed as a result of this reaction that starts in the stroma, the tumour cells being thus provided with a possible means of escape from their in situ localization. This interpretation is in contrast to accepted teaching that the factors that facilitate infiltration are provided by the tumor cells. The observation is also of potential diagnostic interest.